If he can see contrast - go with that if you don't want to ask him. Take a black and white copy of a pattern to see what he sees. Stick to drastic contrast. Maybe you will get brave and present him with the copy or take him with you to the store and allow him to pick out the fabrics. Make sure you write down which fabric will replace the color of fabric for the pattern pictured. It is no fun getting a project home, washing the fabric, then trying to figure out what goes where!
What a wonderful idea. I am sure he will be thrilled. Good luck.
Lilhawk