there are a lot with invisible colors
if you want to add it to the colorset you're using, colorsets are pretty easy to modify
looking at the default colorset as an example:
0.900 0.000 0.000 1.000
0.900 0.900 0.000 1.000
0.000 0.500 0.250 1.000
0.200 0.000 0.800 1.000
0.900 0.900 0.900 1.000
0.750 0.750 0.750 1.000
0.500 0.500 0.500 1.000
0.200 0.200 0.200 1.000
100 50 0 255
DIV:Standard
it's a list of colors in RGBA format, Red Green Blue Alpha, followed by the division name
you can just add a color to that list
to be almost invisible, you want a low alpha
so 0 0 0 5 would be an almost invisible black
255 255 255 5 would be an almost invisible white
or just use 0 0 0 0 or 255 255 255 0 for completely invisible (just like rendering turned off)
note that there are two ways to represent a color, either 0-255 as integers or 0-1 as decimals
higher means more of that value (ie more red or more opaque)
