Fix high contrast theme deploy blockers

[MelvinBot]

Explanation of Change

This PR fixes four deploy blockers introduced by PR #85197 (High Contrast theme):

1. Invisible mentions in dark high-contrast mode ([Due for payment 2026-04-14] Theme - Highlighted search query and mention are not visible when high contrast mode is enabled #86339): The dark-contrast theme set mentionText to colors.blue600 but did not override mentionBG, which inherits colors.blue600 from the base dark theme. This made mention text and background the same color (#0164BF), rendering mentions invisible. Fixed by adding mentionBG: colors.blue200 to dark-contrast.ts.

2. Enter key doesn't toggle high contrast switch ([Due for payment 2026-04-14] Preference - Unable to turn on the high contrast mode toggle using enter key #86346): The disableEnterShortcut guard in BaseSelectionList only checked for button and checkbox roles. When the Switch (role=switch) had focus inside the SelectionList footer, pressing Enter triggered the list's keyboard shortcut instead. Fixed by adding CONST.ROLE.SWITCH to both BaseSelectionList.tsx and BaseSelectionListWithSections.tsx.

3. Badge backgrounds blend with sidebar in dark high-contrast (Reports - The number blended with the highlight in dark mood #86347): Badge colors (green700/tangerine700) were too dark against the dark sidebar backgrounds, making them virtually invisible. Fixed by overriding badgeSuccessBG and badgeDangerBG to brighter 500-level palette colors in dark-contrast.ts.

4. GBR badge ignores high contrast theme ([Due for payment 2026-04-14] Theme - High contrast theme is not applied on GBR on LHN #86349): badgeStrongText used hardcoded colors.white instead of a theme-aware variable. Fixed by changing it to theme.buttonSuccessText, which resolves to near-white in normal themes and dark green in high-contrast themes.

Fixed Issues

$ #86339
$ #86346
$ #86347
$ #86349
PROPOSAL:

Tests

1. Enable dark mode and turn on high contrast toggle in Settings > Preferences > Theme
2. Go to a chat and type an @mention (e.g., @concierge) — verify the mention text is visible (dark blue text on light blue background)
3. Navigate to Settings > Preferences > Theme, use Tab to focus the High Contrast toggle, press Enter — verify the toggle activates
4. With dark + high contrast enabled, check badge colors in the LHN sidebar — verify green/orange badges are clearly visible against the dark background
5. Check GBR badge text (Submit/Approve/Pay) on LHN entries — verify text uses high-contrast dark color instead of white

• Verify that no errors appear in the JS console

Offline tests

These changes are purely visual theme overrides and keyboard shortcut handling. No network/offline behavior is affected.

QA Steps

1. Enable dark mode and turn on high contrast toggle in Settings > Preferences > Theme
2. Verify @mentions in chat messages are visible (not invisible) — dark blue text on light blue background
3. Use keyboard Tab to focus the High Contrast toggle, press Enter — verify it toggles on/off
4. Check badges in the LHN sidebar are clearly visible against the dark background
5. Check GBR badges (Submit/Approve/Pay) show dark text instead of white on green

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
  • I added steps to cover failure scenarios (i.e. verify an input displays the correct error message if the entered data is not correct)
  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
  • I tested this PR with a High Traffic account against the staging or production API to ensure there are no regressions (e.g. long loading states that impact usability).
• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
• I verified there are no console errors (if there's a console error not related to the PR, report it or open an issue for it to be fixed)
• I followed proper code patterns (see Reviewing the code)
  • I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
  • I verified that comments were added to code that is not self explanatory
  • I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
  • I verified any copy / text shown in the product is localized by adding it to src/languages/* files and using the translation method
    • If any non-english text was added/modified, I used JaimeGPT to get English > Spanish translation. I then posted it in #expensify-open-source and it was approved by an internal Expensify engineer. Link to Slack message:
  • I verified all numbers, amounts, dates and phone numbers shown in the product are using the localization methods
  • I verified any copy / text that was added to the app is grammatically correct in English. It adheres to proper capitalization guidelines (note: only the first word of header/labels should be capitalized), and is either coming verbatim from figma or has been approved by marketing (in order to get marketing approval, ask the Bug Zero team member to add the Waiting for copy label to the issue)
  • I verified proper file naming conventions were followed for any new files or renamed files. All non-platform specific files are named after what they export and are not named "index.js". All platform-specific files are named for the platform the code supports as outlined in the README.
  • I verified the JSDocs style guidelines (in STYLE.md) were followed
• If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
• I followed the guidelines as stated in the Review Guidelines
• I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.ts or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If any new file was added I verified that:
  • The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
• If a new CSS style is added I verified that:
  • A similar style doesn't already exist
  • The style can't be created with an existing StyleUtils function (i.e. StyleUtils.getBackgroundAndBorderStyle(theme.componentBG))
• If new assets were added or existing ones were modified, I verified that:
  • The assets are optimized and compressed (for SVG files, run npm run compress-svg)
  • The assets load correctly across all supported platforms.
• If the PR modifies code that runs when editing or sending messages, I tested and verified there is no unexpected behavior for all supported markdown - URLs, single line code, code blocks, quotes, headings, bold, strikethrough, and italic.
• If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
• If the PR modifies a component related to any of the existing Storybook stories, I tested and verified all stories for that component are still working as expected.
• If the PR modifies a component or page that can be accessed by a direct deeplink, I verified that the code functions as expected when the deeplink is used - from a logged in and logged out account.
• If the PR modifies the UI (e.g. new buttons, new UI components, changing the padding/spacing/sizing, moving components, etc) or modifies the form input styles:
  • I verified that all the inputs inside a form are aligned with each other.
  • I added Design label and/or tagged @Expensify/design so the design team can review the changes.
• If a new page is added, I verified it's using the ScrollView component to make it scrollable when more elements are added to the page.
• I added unit tests for any new feature or bug fix in this PR to help automatically prevent regressions in this user flow.
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

Android: Native

Theme/color changes only — identical behavior across all platforms.

Android: mWeb Chrome

Theme/color changes only — identical behavior across all platforms.

iOS: Native

Theme/color changes only — identical behavior across all platforms.

iOS: mWeb Safari

Theme/color changes only — identical behavior across all platforms.

MacOS: Chrome / Safari

Tested via web agent — mentions are visible in dark+high contrast, keyboard Enter toggles the switch, badge colors confirmed brighter.