afni.nimh.nih.gov

The builtin colorscales are not in a file, but you can set one of them as a default by using its name - the same name as on the menu.

Colors are defined by RGB triples; (0,0,0) is pure black, but is used to define a "no color" or "gap" in the colorscale. If you do want to overlay black, use something like (1,1,1), which is pretty dark - (255,255,255) is white.

bob cox