If you have a VGA machine, you are restricted to displaying at most 256 colors at a time. These 256 colors are held in a palette. You can choose the palette colors from a range of 262,144 colors (256K), but only 256 at a time. The palette routines REMAPPALETTERGB and REMAPALLPALETTERGB assign Red-Green-Blue (RGB) colors to palette indexes.
Functions and subroutines that use color indexes create graphic outputs that depend on the mapping between palette indexes and RGB colors. REMAPPALETTERGB remaps one color index to an RGB color, and REMAPALLPALETTERGB remaps the entire palette, up to 236 colors, (20 colors are reserved by the system). You cannot remap the palette on machines capable of displaying 20 colors or fewer.
SVGA and true color video adapters are capable of displaying 262,144 (256K) colors and 16.7 million colors respectively. If you use a palette, you are restricted to the colors available in the palette.
To access the entire set of available colors, not just the 256 or fewer colors in the palette, you should use functions that specify a color value directly. These functions end in RGB and use Red-Green-Blue color values, not indexes to a palette. For example, SETCOLORRGB, SETTEXTCOLORRGB, and SETPIXELRGB specify a direct color value, while SETCOLOR, SETTEXTCOLOR, and SETPIXEL each specify a palette color index. If you are displaying more than 256 colors simultaneously, you need to use the RGB direct color value functions exclusively.
To set the physical display properties of your monitor, open the Control Panel and click the Display icon.
QuickWin only supports a 256-color pallette, regardless of the number of colors set for the monitor.
For more information on setting colors, see Adding Color in Drawing Graphics Elements.