Colors are specified in ProXL as color(R,G,B) terms,
where R, G, and B are (usually floating point)
numbers
between 0 and 1 inclusive. Alternately, a color can be specified as
an atom naming a color (case is not significant), such as blue
or plum, or as an atom of
the form '#RGB' or '#RRGGBB' or '#RRRGGGBBB' or
'#RRRRGGGGBBBB' where R, G, and B are hex digits. For example,
'#05F' would represent a color with no red, 5/15 (or 0.333333)
green, and full blue. In put_color
and put_colors, Red, Green, and/or Blue in a color(Red,Green,Blue)
term can be the atom none, which means that that primary won't be
changed in the colormap.
Pixel values are simply integers.