I've had the same thing happen to me with hackberry. Question for ya, are these drying in a dark place? I've noticed that hackberry cured in my garage without sunlight turned colors and the couple pieces I left out in front of the garage under the overhang a couple days. Big difference in color. Here are some shots of my weird colored ones.
And this is what it turned into...
I love hackberry and would not hesitate to use what you have got, I've got tons of the stuff laying in the garage just waiting to become a bow. Love this stuff and best of luck on the bows.
Kip