simple program to determine the color string in hex by clicking on a pixel

 grabc is simple but useful program to determine the color string in
 hex or in RGB components by clicking on a pixel on the screen.
 When this program is run, the mouse pointer is grabbed and changed to
 a cross hair and when the mouse is clicked, the color of the clicked
 pixel is written to stdout in hex and the R, G, B components are
 written to stderr.
 .
 This program can be useful when you see a color and want to use the
 color in xterm or your window manager's border but no clue what the
 name of the color is. It's silly to use a image processing software
 to find it out.