I've got a lot of exp dying G10, FRN and Benchmades polymer it uses on the griptilian line (whatever its trade name is). I use liquid and/or powder RiT dye (no difference, some colors are one and some are the other, you can even mix them together). I mix the liquid dye per instructions but I add one cup of vinegar. I mix the powder per instructions but I use a 50% water 50% vinegar mix for the total amount of water it calls for.
The longer you leave it in darkens the color so there is no set time. After you dye it rinse it in boiling water for 5 min.
I have found spyderco's FRN and [any] G10 to hold the color the best, on my mini grip, it doesn't wash but the handle scratches easier and anything more than a paper width deep and you'll scratch threw the color. FRN and G10 seem to be more resilient in that I've never needed to re-dye anything I've done of either of those materials, I have to re-dye my mini grip about every 6 months. I used a custom mixed color on my mini grip but that's ok cause I just save th dye in a gatoraid bottle, it keeps just fine at room temp.
I know for a fact it'll hold up to being submerged for 5 minutes in both gas and alcohol yet the rit color remover claims to work of you want to redo it or go back to stock (seen people here say that too but never tried it).