Colors

There's no way of telling how many colorcells are unallocated.

Your program should work on both monochrome and color screens if possible using something like the following code.

Bool iscolor;
Xcolor blue;
iscolor = (XDisplayCells(display, screen)>2);
foreground = (iscolor &&
              XParsecolor(display,cmap, "blue",&blue) &&
              XAllocColor(display,cmap, &blue))
                    ? blue.pixel : BlackPixel (display,screen));