the number of the color register to set. Ranges from 0 to 31 on current Amiga displays.
r
red level (0-15)
g
green level (0-15)
b
blue level (0-15)
RESULT
Store the (r,g,b) triplet at index n of the ColorMap structure. This function can be used to set up a ColorMap before before linking it into a viewport.