Coloring And "sealing" Vellum Parchment?

[Skald]

I'll get myself some parchment, or "vellum". Probably from calf or goat skin. I intend to try make a lamp out of it, i.e. sew it to a wooden frame. I want to paint it for decoration, but I have no idea what kind of dye/ink I should be using. And I guess I need to put some finish on it for "sealing" it, as parchment gets stained pretty easy, even from touching it with your bare fingers, and just some few unintentional stains of any fluid (like water) might ruin it.

So, does anyone have any experience from this kind of leather material? What on earth should I be using? I've tried to "google" it, but come up with almost solely pages dealing with fake "parchment" made of paper, meant to be looking like the real deal.