I use garment leather for most all my backings now. You can find it in any color/thickness that your project calls for. For the most part it’s already treated, and won’t wear off on clothing. I have used backings that I have had to dye, but even with a few seal coats, over time, it will still bleed on to the wearers clothes. As far as source, Tandy, and Weaver leather have plenty of color, and skin choices. For anything I want to have a more unique/weird look, I scower the internet until I find something close to what I’m looking for.
hope this helps, man!
And thank you for your kind words, by the way!