Dying is very fun! (Coloring I mean, not actually dying, that'd suck

) You can't do black as far as I know but you can do the other colors. The lighter the color the better the dye will work in my experience.
I think everyone has their own way if doing it but I'll tell you how I do it.
1. Make your your g10 is clean of course. Give it a good scrubbing.
2. buy some Rit dye in whatever color you like. I guess that would actually come first but whatever.
3. fill a small saucepan about three quarters of the way full with water and bring it to the point where it's just starting to boil.
4. add your dye. I use just a tin bit (about one tablespoon) and stir it.
5. Put your g10 into the water. It's best to have some wire or paracord going through the lanyard holes so you can stir the g10 around and take it out easier.
6. stir the g10 around in the dye slowly until you have your desired color. it usually takes about five minutes for me.
7. remove the g10 and wash it off with water.
That's pretty much it. I hope that makes sense. Here are some of my knives I have dyed using that system.
Ball cage
All of those knives were dyed with the same packet of rit dye and I still have a bunch left.