I bought a mini Grip with white scales from Benchmade 2-3 years ago, and it has been my go-to EDC for most of that time. I’ve also never cleaned it. There is some discoloration, but it looks to be the result of the accumulation of skin oils (i.e. yellowish)—particularly in the ridges of the textured areas, which makes sense. There is a tiny, tiny bit of darker/greyish discoloration, but it’s really insignificant.
10 minutes with some soap and a toothbrush would probably restore it back to its former glory (or close). (If I get around to that this weekend, I’ll try to post some before and after pics. Apologies if I’m overcome by laziness.)