A texture based method of choosing a color from Unity's built in GUI API. Idea taken and improved upon from the Unity Forum post found here: http://forum.unity3d.com/threads/32760-Making-a-color-wheel-color-picker?p=213734

Usage:
1. Drag and drop the "ColorPicker" prefab into your scene.
2. Bring up the inspector for the ColorPicker.
3. Set the "Loc X" and "Loc Y" variables to the coordinates you would like the Color Picker to appear on the screen.
4. Add "hooks" to the Color Picker in your GUI code (see Demo Scene and GUIExample.cs on how to accomplish this)