How do I get the user-selected Windows color scheme color for anything?

Just use the Windows API function GetSysColor:


nIndex can be:

COLOR_3DDKSHADOW Dark shadow for three-dimensional display elements.
COLOR_3DFACE, COLOR_BTNFACE Face color for three-dimensional display elements and for dialog box backgrounds.
COLOR_3DHILIGHT, COLOR_3DHIGHLIGHT, COLOR_BTNHILIGHT, COLOR_BTNHIGHLIGHT Highlight color for three-dimensional display elements (for edges facing the light source.)
COLOR_3DLIGHT Light color for three-dimensional display elements (for edges facing the light source.)
COLOR_3DSHADOW, COLOR_BTNSHADOW Shadow color for three-dimensional display elements (for edges facing away from the light source).
COLOR_ACTIVEBORDER Active window border.
COLOR_ACTIVECAPTION Active window title bar.
Windows 98, Windows 2000: Specifies the left side color in the color gradient of an active window's title bar if the gradient effect is enabled.

COLOR_APPWORKSPACE Background color of multiple document interface (MDI) applications.
COLOR_BACKGROUND, COLOR_DESKTOP Desktop.
COLOR_BTNTEXT Text on push buttons.
COLOR_CAPTIONTEXT Text in caption, size box, and scroll bar arrow box.
COLOR_GRADIENTACTIVECAPTION Windows 98, Windows 2000: Right side color in the color gradient of an active window's title bar. COLOR_ACTIVECAPTION specifies the left side color. Use SPI_GETGRADIENTCAPTIONS with the SystemParametersInfo function to determine whether the gradient effect is enabled.
COLOR_GRADIENTINACTIVECAPTION Windows 98, Windows 2000: Right side color in the color gradient of an inactive window's title bar. COLOR_INACTIVECAPTION specifies the left side color.
COLOR_GRAYTEXT Grayed (disabled) text. This color is set to 0 if the current display driver does not support a solid gray color.
COLOR_HIGHLIGHT Item(s) selected in a control.
COLOR_HIGHLIGHTTEXT Text of item(s) selected in a control.
COLOR_HOTLIGHT Windows 98, Windows 2000: Color for a hot-tracked item. Single clicking a hot-tracked item executes the item.
COLOR_INACTIVEBORDER Inactive window border.
COLOR_INACTIVECAPTION Inactive window caption.
Windows 98, Windows 2000: Specifies the left side color in the color gradient of an inactive window's title bar if the gradient effect is enabled.

COLOR_INACTIVECAPTIONTEXT Color of text in an inactive caption.
COLOR_INFOBK Background color for tooltip controls.
COLOR_INFOTEXT Text color for tooltip controls.
COLOR_MENU Menu background.
COLOR_MENUHILIGHT Whistler: The color used to highlight menu items when the menu appears as a flat menu (see SystemParametersInfo). The highlighted menu item is outlined with COLOR_HIGHLIGHT.
COLOR_MENUBAR Whistler: The background color for the menu bar when menus appear as flat menus (see SystemParametersInfo). However, COLOR_MENU continues to specify the background color of the menu popup.
COLOR_MENUTEXT Text in menus.
COLOR_SCROLLBAR Scroll bar gray area.
COLOR_WINDOW Window background.
COLOR_WINDOWFRAME Window frame.
COLOR_WINDOWTEXT Text in windows.

The values for these are:
(Taken from winuser.h)
#define COLOR_SCROLLBAR 0
#define COLOR_BACKGROUND 1
#define COLOR_ACTIVECAPTION 2
#define COLOR_INACTIVECAPTION 3
#define COLOR_MENU 4
#define COLOR_WINDOW 5
#define COLOR_WINDOWFRAME 6
#define COLOR_MENUTEXT 7
#define COLOR_WINDOWTEXT 8
#define COLOR_CAPTIONTEXT 9
#define COLOR_ACTIVEBORDER 10
#define COLOR_INACTIVEBORDER 11
#define COLOR_APPWORKSPACE 12
#define COLOR_HIGHLIGHT 13
#define COLOR_HIGHLIGHTTEXT 14
#define COLOR_BTNFACE 15
#define COLOR_BTNSHADOW 16
#define COLOR_GRAYTEXT 17
#define COLOR_BTNTEXT 18
#define COLOR_INACTIVECAPTIONTEXT 19
#define COLOR_BTNHIGHLIGHT 20

#if(WINVER >= 0x0400)
#define COLOR_3DDKSHADOW 21
#define COLOR_3DLIGHT 22
#define COLOR_INFOTEXT 23
#define COLOR_INFOBK 24
#endif /* WINVER >= 0x0400 */

#if(WINVER >= 0x0500)
#define COLOR_HOTLIGHT 26
#define COLOR_GRADIENTACTIVECAPTION 27
#define COLOR_GRADIENTINACTIVECAPTION 28
#endif /* WINVER >= 0x0500 */

#if(WINVER >= 0x0400)
#define COLOR_DESKTOP COLOR_BACKGROUND
#define COLOR_3DFACE COLOR_BTNFACE
#define COLOR_3DSHADOW COLOR_BTNSHADOW
#define COLOR_3DHIGHLIGHT COLOR_BTNHIGHLIGHT
#define COLOR_3DHILIGHT COLOR_BTNHIGHLIGHT
#define COLOR_BTNHILIGHT COLOR_BTNHIGHLIGHT
#endif /* WINVER >= 0x0400 */