NAME
       SetRGB4CM -- Set one color register for this ColorMap.

   SYNOPSIS
       SetRGB4CM(  cm,  n,   r,    g,    b)
                   a0  d0  d1:4  d2:4  d3:4

       void SetRGB4CM( struct ColorMap *, SHORT, UBYTE, UBYTE, UBYTE );

   INPUTS
	cm = colormap
       n = 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.

   BUGS

   SEE ALSO
       GetColorMap() GetRGB4() SetRGB4() graphics/view.h