I thought I'd get back to you, since about 5 months have passed since I first posted that I had less gray hair. It's hard to measure, since the hair color change is so gradual, but I really think my overall hair color has become yet darker since I first posted about this. I still catch myself admiring my hair color in the bathroom mirror. I'm sure my friends must think I started coloring my hair.
I still have gray hair, just much less. I'm sure this is only a mirror of internal changes for the better since I started OP. I use coconut oil every day, as well as sometimes doing a second pull with sesame oil. In my ignorance, I actually started OPing with regular, grocery store quality canola oil, then I switched to non-organic, non-expeller pressed olive oil (the only olive oil available where I live) Even then I was seeing many different health changes for the better.
I hope you stayed with oil pulling and that you have noticed a few less gray hairs.