I've been using Derm for probably around 4 years or so, but only recently front to back as opposed to just back. Diffuse loss is a pisser. Anyway, I've noticed in the latest batch that the Medium Brown has given me a slight red tinge to it, a bit like that McCartney dyed hair look. The one old men sometimes have when it's been really badly done. I do have a bit more grey hair on my head in spurts than I did 4 years ago, but it can't be that can it? Anyone use a Dark Brown on their medium ish brown hair, out of interest. I've never bought the dark one. Or have they changed formula, or otherwise. I do find some parts of the head don't go brown when applied, and still see the scalp, It's not what it was.