Hi, I don't have a lot of experience with hickory. I tried using regular wood stain on two bows, but got almost no penetration and very light color. One bow I stained with brown leather dye applied and lightly sanded. It has a nice dark color and looks good under a Tung oil finish, but it does show scratches. I saw a hickory bow today that had a heat treated back, which gave a nice mottled appearance. If you're feeling artistic you could paint the back of your bow , as many west coast tribes did, or even try a camo effect.
Hopefully others with more experience can give additional suggestions. Ron