[FEATURE] Add light theme

Dashboard/App.xaml.cs

@@ -37,6 +37,10 @@ protected override void OnStartup(StartupEventArgs e)
 
             base.OnStartup(e);
 
+            // Apply saved color theme before the main window is shown
+            var prefs = new Services.UserPreferencesService().GetPreferences();
+            ThemeManager.Apply(prefs.ColorTheme ?? "Dark");
+
             // Register global exception handlers
             AppDomain.CurrentDomain.UnhandledException += OnUnhandledException;
             DispatcherUnhandledException += OnDispatcherUnhandledException;

Dashboard/Controls/AlertsHistoryContent.xaml

@@ -7,10 +7,6 @@
              d:DesignHeight="450" d:DesignWidth="800">
     <UserControl.Resources>
         <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceDictionary Source="pack://application:,,,/Themes/DarkTheme.xaml"/>
-            </ResourceDictionary.MergedDictionaries>
-
             <!-- Context Menu for DataGrid Copy/Export -->
             <ContextMenu x:Key="DataGridContextMenu">
                 <MenuItem Header="Copy Cell" Click="CopyCell_Click">
@@ -74,7 +70,7 @@
                 <ComboBoxItem Content="All Servers" IsSelected="True"/>
             </ComboBox>
             <Button Content="Refresh" Click="RefreshButton_Click" Margin="12,0,0,0" Padding="10,4" MinWidth="70"
-                    Style="{StaticResource SuccessButton}"/>
+                    Style="{DynamicResource SuccessButton}"/>
             <Button x:Name="DismissSelectedButton" Content="Dismiss Selected" Click="DismissSelected_Click"
                     Margin="8,0,0,0" Padding="10,4" MinWidth="90" IsEnabled="False"/>
             <Button Content="Dismiss All" Click="DismissAll_Click"

Dashboard/Controls/CriticalIssuesContent.xaml

@@ -8,10 +8,6 @@
              d:DesignHeight="450" d:DesignWidth="800">
     <UserControl.Resources>
         <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceDictionary Source="pack://application:,,,/Themes/DarkTheme.xaml"/>
-            </ResourceDictionary.MergedDictionaries>
-
             <!-- Context Menu for DataGrid Copy/Export -->
             <ContextMenu x:Key="DataGridContextMenu">
                 <MenuItem Header="Copy Cell" Click="CopyCell_Click">

Dashboard/Controls/DailySummaryContent.xaml

@@ -8,10 +8,6 @@
              d:DesignHeight="450" d:DesignWidth="800">
     <UserControl.Resources>
         <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceDictionary Source="pack://application:,,,/Themes/DarkTheme.xaml"/>
-            </ResourceDictionary.MergedDictionaries>
-
             <!-- Context Menu for DataGrid Copy/Export -->
             <ContextMenu x:Key="DataGridContextMenu">
                 <MenuItem Header="Copy Cell" Click="CopyCell_Click">
@@ -43,9 +39,9 @@
         <!-- Date Selection Controls -->
         <StackPanel Grid.Row="0" Orientation="Horizontal" Margin="10,5" Background="{DynamicResource BackgroundLightBrush}" Height="40">
             <TextBlock Text="Summary Date:" VerticalAlignment="Center" Margin="5,0" FontWeight="Bold"/>
-            <Button x:Name="DailySummaryTodayButton" Content="Today" Click="DailySummaryToday_Click" Margin="5,0" Padding="8,4" MinWidth="60" Style="{StaticResource AccentButton}"/>
+            <Button x:Name="DailySummaryTodayButton" Content="Today" Click="DailySummaryToday_Click" Margin="5,0" Padding="8,4" MinWidth="60" Style="{DynamicResource AccentButton}"/>
             <DatePicker x:Name="DailySummaryDatePicker" Width="120" Margin="5,0" SelectedDateChanged="DailySummaryDate_Changed" CalendarOpened="DatePicker_CalendarOpened"/>
-            <Button Content="Refresh" Click="DailySummary_Refresh_Click" Margin="10,0,2,0" Padding="10,4" MinWidth="70" Style="{StaticResource SuccessButton}"/>
+            <Button Content="Refresh" Click="DailySummary_Refresh_Click" Margin="10,0,2,0" Padding="10,4" MinWidth="70" Style="{DynamicResource SuccessButton}"/>
             <TextBlock x:Name="DailySummaryIndicator"
                        Text="Showing: Today"
                        Margin="10,0"

Dashboard/Controls/DailySummaryContent.xaml.cs

@@ -145,15 +145,15 @@ private void DatePicker_CalendarOpened(object sender, RoutedEventArgs e)
                     var popup = datePicker.Template.FindName("PART_Popup", datePicker) as System.Windows.Controls.Primitives.Popup;
                     if (popup?.Child is System.Windows.Controls.Calendar calendar)
                     {
-                        TabHelpers.ApplyDarkThemeToCalendar(calendar);
+                        TabHelpers.ApplyThemeToCalendar(calendar);
                     }
                     else
                     {
                         // Fallback: search visual tree
                         var calendar2 = FindVisualChild<System.Windows.Controls.Calendar>(datePicker);
                         if (calendar2 != null)
                         {
-                            TabHelpers.ApplyDarkThemeToCalendar(calendar2);
+                            TabHelpers.ApplyThemeToCalendar(calendar2);
                         }
                     }
                 }), System.Windows.Threading.DispatcherPriority.Loaded);

Dashboard/Controls/LandingPage.xaml

@@ -6,14 +6,6 @@
              xmlns:local="clr-namespace:PerformanceMonitorDashboard.Controls"
              mc:Ignorable="d"
              d:DesignHeight="600" d:DesignWidth="1000">
-    <UserControl.Resources>
-        <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceDictionary Source="pack://application:,,,/Themes/DarkTheme.xaml"/>
-            </ResourceDictionary.MergedDictionaries>
-        </ResourceDictionary>
-    </UserControl.Resources>
-
     <Grid Background="{DynamicResource BackgroundBrush}">
         <Grid.RowDefinitions>
             <RowDefinition Height="Auto"/>

Dashboard/Controls/MemoryContent.xaml

@@ -9,10 +9,6 @@
              d:DesignHeight="600" d:DesignWidth="1200">
     <UserControl.Resources>
         <ResourceDictionary>
-            <ResourceDictionary.MergedDictionaries>
-                <ResourceDictionary Source="pack://application:,,,/Themes/DarkTheme.xaml"/>
-            </ResourceDictionary.MergedDictionaries>
-
             <!-- Context Menu for DataGrid Copy/Export -->
             <ContextMenu x:Key="DataGridContextMenu">
                 <MenuItem Header="Copy Cell" Click="CopyCell_Click">

Dashboard/Controls/MemoryContent.xaml.cs

@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright (c) 2026 Erik Darling, Darling Data LLC
  *
  * This file is part of the SQL Server Performance Monitor.
@@ -81,14 +81,16 @@ public MemoryContent()
             InitializeComponent();
             SetupChartContextMenus();
             Loaded += OnLoaded;
+            Helpers.ThemeManager.ThemeChanged += OnThemeChanged;
+            Unloaded += (_, _) => Helpers.ThemeManager.ThemeChanged -= OnThemeChanged;
 
             // Apply dark theme immediately so charts don't flash white before data loads
-            TabHelpers.ApplyDarkModeToChart(MemoryStatsOverviewChart);
-            TabHelpers.ApplyDarkModeToChart(MemoryGrantSizingChart);
-            TabHelpers.ApplyDarkModeToChart(MemoryGrantActivityChart);
-            TabHelpers.ApplyDarkModeToChart(MemoryClerksChart);
-            TabHelpers.ApplyDarkModeToChart(PlanCacheChart);
-            TabHelpers.ApplyDarkModeToChart(MemoryPressureEventsChart);
+            TabHelpers.ApplyThemeToChart(MemoryStatsOverviewChart);
+            TabHelpers.ApplyThemeToChart(MemoryGrantSizingChart);
+            TabHelpers.ApplyThemeToChart(MemoryGrantActivityChart);
+            TabHelpers.ApplyThemeToChart(MemoryClerksChart);
+            TabHelpers.ApplyThemeToChart(PlanCacheChart);
+            TabHelpers.ApplyThemeToChart(MemoryPressureEventsChart);
 
             _memoryStatsOverviewHover = new Helpers.ChartHoverHelper(MemoryStatsOverviewChart, "MB");
             _memoryGrantSizingHover = new Helpers.ChartHoverHelper(MemoryGrantSizingChart, "MB");
@@ -103,6 +105,19 @@ private void OnLoaded(object sender, RoutedEventArgs e)
             // No grids to configure - all tabs are chart-only now
         }
 
+        private void OnThemeChanged(string _)
+        {
+            foreach (var field in GetType().GetFields(
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance))
+            {
+                if (field.GetValue(this) is ScottPlot.WPF.WpfPlot chart)
+                {
+                    Helpers.TabHelpers.ApplyThemeToChart(chart);
+                    chart.Refresh();
+                }
+            }
+        }
+
         private void SetupChartContextMenus()
         {
             // Memory Stats Overview chart
@@ -212,7 +227,7 @@ private void LoadMemoryStatsOverviewChart(List<MemoryStatsItem> memoryData, int
             }
             MemoryStatsOverviewChart.Plot.Clear();
             _memoryStatsOverviewHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(MemoryStatsOverviewChart);
+            TabHelpers.ApplyThemeToChart(MemoryStatsOverviewChart);
 
             var dataList = memoryData?.OrderBy(d => d.CollectionTime).ToList() ?? new List<MemoryStatsItem>();
             // Total Memory series with gap filling
@@ -487,7 +502,7 @@ private void LoadMemoryGrantSizingChart(List<PoolGrantPoint> aggregated, int hou
             }
             MemoryGrantSizingChart.Plot.Clear();
             _memoryGrantSizingHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(MemoryGrantSizingChart);
+            TabHelpers.ApplyThemeToChart(MemoryGrantSizingChart);
 
             var poolIds = aggregated.Select(d => d.PoolId).Distinct().OrderBy(id => id).ToList();
             int colorIndex = 0;
@@ -556,7 +571,7 @@ private void LoadMemoryGrantActivityChart(List<PoolGrantPoint> aggregated, int h
             }
             MemoryGrantActivityChart.Plot.Clear();
             _memoryGrantActivityHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(MemoryGrantActivityChart);
+            TabHelpers.ApplyThemeToChart(MemoryGrantActivityChart);
 
             var poolIds = aggregated.Select(d => d.PoolId).Distinct().OrderBy(id => id).ToList();
             int colorIndex = 0;
@@ -727,7 +742,7 @@ private async System.Threading.Tasks.Task UpdateMemoryClerksChartFromPickerAsync
                 }
                 MemoryClerksChart.Plot.Clear();
                 _memoryClerksHover?.Clear();
-                TabHelpers.ApplyDarkModeToChart(MemoryClerksChart);
+                TabHelpers.ApplyThemeToChart(MemoryClerksChart);
 
                 DateTime rangeEnd = _memoryClerksToDate ?? Helpers.ServerTimeHelper.ServerNow;
                 DateTime rangeStart = _memoryClerksFromDate ?? rangeEnd.AddHours(-_memoryClerksHoursBack);
@@ -864,7 +879,7 @@ private void LoadPlanCacheChart(IEnumerable<PlanCacheStatsItem> data, int hoursB
             }
             PlanCacheChart.Plot.Clear();
             _planCacheHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(PlanCacheChart);
+            TabHelpers.ApplyThemeToChart(PlanCacheChart);
 
             var dataList = data?.ToList() ?? new List<PlanCacheStatsItem>();
             if (dataList.Count > 0)
@@ -1005,7 +1020,7 @@ private void LoadMemoryPressureEventsChart(IEnumerable<MemoryPressureEventItem>
             }
             MemoryPressureEventsChart.Plot.Clear();
             _memoryPressureEventsHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(MemoryPressureEventsChart);
+            TabHelpers.ApplyThemeToChart(MemoryPressureEventsChart);
 
             // Only chart HIGH severity events
             var dataList = data?.Where(d => d.Severity.Equals("HIGH", StringComparison.OrdinalIgnoreCase))

Dashboard/Controls/QueryPerformanceContent.xaml.cs

@@ -1,4 +1,4 @@
-/*
+/*
  * Copyright (c) 2026 Erik Darling, Darling Data LLC
  *
  * This file is part of the SQL Server Performance Monitor.
@@ -133,6 +133,7 @@ public QueryPerformanceContent()
             SetupChartSaveMenus();
             Loaded += OnLoaded;
             Unloaded += OnUnloaded;
+            Helpers.ThemeManager.ThemeChanged += OnThemeChanged;
 
             _queryDurationHover = new Helpers.ChartHoverHelper(QueryPerfTrendsQueryChart, "ms/sec");
             _procDurationHover = new Helpers.ChartHoverHelper(QueryPerfTrendsProcChart, "ms/sec");
@@ -169,15 +170,30 @@ private void OnUnloaded(object sender, RoutedEventArgs e)
             _queryStoreUnfilteredData = null;
             _qsRegressionsUnfilteredData = null;
             _lrqPatternsUnfilteredData = null;
+
+            Helpers.ThemeManager.ThemeChanged -= OnThemeChanged;
+        }
+
+        private void OnThemeChanged(string _)
+        {
+            foreach (var field in GetType().GetFields(
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance))
+            {
+                if (field.GetValue(this) is ScottPlot.WPF.WpfPlot chart)
+                {
+                    Helpers.TabHelpers.ApplyThemeToChart(chart);
+                    chart.Refresh();
+                }
+            }
         }
 
         private void OnLoaded(object sender, RoutedEventArgs e)
         {
             // Initialize charts with dark mode immediately (before data is loaded)
-            TabHelpers.ApplyDarkModeToChart(QueryPerfTrendsQueryChart);
-            TabHelpers.ApplyDarkModeToChart(QueryPerfTrendsProcChart);
-            TabHelpers.ApplyDarkModeToChart(QueryPerfTrendsQsChart);
-            TabHelpers.ApplyDarkModeToChart(QueryPerfTrendsExecChart);
+            TabHelpers.ApplyThemeToChart(QueryPerfTrendsQueryChart);
+            TabHelpers.ApplyThemeToChart(QueryPerfTrendsProcChart);
+            TabHelpers.ApplyThemeToChart(QueryPerfTrendsQsChart);
+            TabHelpers.ApplyThemeToChart(QueryPerfTrendsExecChart);
             QueryPerfTrendsQueryChart.Refresh();
             QueryPerfTrendsProcChart.Refresh();
             QueryPerfTrendsQsChart.Refresh();
@@ -1594,7 +1610,7 @@ private void LoadDurationChart(WpfPlot chart, IEnumerable<DurationTrendItem> tre
                 }
                 chart.Plot.Clear();
                 hover?.Clear();
-                TabHelpers.ApplyDarkModeToChart(chart);
+                TabHelpers.ApplyThemeToChart(chart);
 
                 var dataList = (trendData ?? Enumerable.Empty<DurationTrendItem>())
                     .OrderBy(d => d.CollectionTime)
@@ -1649,7 +1665,7 @@ private void LoadExecChart(IEnumerable<ExecutionTrendItem> execTrends, int hours
             }
             QueryPerfTrendsExecChart.Plot.Clear();
             _execTrendsHover?.Clear();
-            TabHelpers.ApplyDarkModeToChart(QueryPerfTrendsExecChart);
+            TabHelpers.ApplyThemeToChart(QueryPerfTrendsExecChart);
 
             var dataList = (execTrends ?? Enumerable.Empty<ExecutionTrendItem>())
                 .OrderBy(d => d.CollectionTime)

Dashboard/Controls/ResourceMetricsContent.xaml

@@ -112,7 +112,7 @@
                         </Grid.RowDefinitions>
                         <StackPanel Grid.Row="0" Orientation="Horizontal" Margin="5,5,5,2">
                             <TextBlock Text="Select Wait Types" FontWeight="Bold" VerticalAlignment="Center" Foreground="{DynamicResource ForegroundBrush}"/>
-                            <Button Content="Refresh" Click="WaitStatsDetail_Refresh_Click" Margin="10,0,0,0" Padding="8,2" Style="{StaticResource SuccessButton}" FontSize="11"/>
+                            <Button Content="Refresh" Click="WaitStatsDetail_Refresh_Click" Margin="10,0,0,0" Padding="8,2" Style="{DynamicResource SuccessButton}" FontSize="11"/>
                         </StackPanel>
                         <StackPanel Grid.Row="1" Orientation="Horizontal" Margin="5,2">
                             <Button Content="Top Waits" Click="WaitTypes_SelectAll_Click" Padding="6,2" FontSize="10" Margin="0,0,5,0"/>
@@ -299,7 +299,7 @@
                         </Grid.RowDefinitions>
                         <StackPanel Grid.Row="0" Orientation="Horizontal" Margin="5,5,5,2">
                             <TextBlock Text="Select Counters" FontWeight="Bold" VerticalAlignment="Center" Foreground="{DynamicResource ForegroundBrush}"/>
-                            <Button Content="Refresh" Click="PerfmonCounters_Refresh_Click" Margin="10,0,0,0" Padding="8,2" Style="{StaticResource SuccessButton}" FontSize="11"/>
+                            <Button Content="Refresh" Click="PerfmonCounters_Refresh_Click" Margin="10,0,0,0" Padding="8,2" Style="{DynamicResource SuccessButton}" FontSize="11"/>
                         </StackPanel>
                         <ComboBox Grid.Row="1" x:Name="PerfmonPackCombo"
                                   SelectionChanged="PerfmonPack_SelectionChanged"