1) Take the scales off the knife.
2) Wash with a brush and Dawn soap.
3) Grab some liquid RIT dye in your desired color.
4) Use the whole bottle and a bout a quart of water in a stainless steel pan. (stainless is important! You'll discover why later)
5) Bring the dye to a low simmer (no need to boil it vigorously) and drop the scales in.
6) Walk away for about 15 minutes, come back and recheck. Rinse off in HOT water and check the color.
7) If the color is to your liking, rinse and scrub with Dawn and COLD water. If not, simmer for some more time. Repeat step 6 until it's what you like.
8) Wash out the pan really, really well so the wife doesn't kill you (unless you enjoy being eviscerated with the knife you just customized).