The XPM specification allows the use of symbolic color names
   in the xpm. For example, if your pixmap should display a symbol of a button, the
   button could have the real button colors: light shadow, dark
   shadow and the normal flat surface color. The only thing you would have to do
   is writing something like this:
   
/* XPM */
static char * button[] = {
"16 16 3 1",
". s foreground",
"X s lightshadow",
"X s darkshadow",
"...pixels here"
}; | 
  
   Unfortunately, the Gtk, unlike CDE, does not support symbolic color names. So
   you cannot use them unless you define your own names and write a function which
   replaces the symbolic names by real colors.
  
   Pixmaps are nice, but what if you want to display a jpg or
   png image? As the gtk libraries don't support this, you could
   use the gd or gd2 to transform the image
   to xpm format and go on with the normal xpm functions.