If you're thinking of "rainbowing" the things, I'd be hesitant - the anodizing process on aluminum and titanium differ considerably. I believe titanium (interference) colors are derived by refraction variations through a very thin layer of titanium oxide. I don't know how this would work on a grip surface.
I believe the Kershaw / Ken Onion rainbow leek is not actually anodized ti but coated stainless.
If I had to have grips like that, I'd probably post on Ken Onion's forum and / or bladeforums - the knife scale people seem to have had some practice in the area. Knife scales would require similar "wearability" to grip panels, I would guess.
Rats! Now you've got me thinking of Devon Thomas damascus grips, maybe with Caspian parts - guess it's time to start buying lotto tickets.
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