the light???? if you talking about the light, I use a blue one.....from extreme in an extreme housing, with green fiber optic....works great.....
I just bought one of those now TruGlo lights with the rheostat and put it on my copperjohn. It is a purple light and the rheostat makes the brightness adjustable. I had a trophy ridge before and used there light it was blue, both worked well for me.
Knobby, The fiber is blue almost clear. It makes a nice blue aiming dot when the light is turned on. Without the light on, I don't think you can see the blue dot.