Fiebing is a leather dye company that your local Tandy leather store will sell. They offer a DEGLAZER that will remove the clear protective finish that most leather has. Then you can re-dye it the color you want and put a coat of finish back on it.
I have never used this on rawhide before but assume it will work all the same. Contact a tandy store and the salesperson should know right off.
So what you will need is--
Deglazer, Dye, and a waterproofing finish such as Top Coat or Super sheen.
All fiebings products that I have used. I am sure there are other good products as well.