Here is the method I used (which I tried AFTER I did RIT dye, which did not work at all and was very frustrating).
I take the hair and lay it out flat on some paper. Then I take a black permanent Sharpie, and colour the hair to a certain length (I have to think about how much will show once I've knotted the end and pulled the plug back through the hole). Then I colour over the black with a brown permanent Sharpie, and I play around with the two markers until I get what looks like
a good "roots" shade. Then I let it sit for a while, then I wash the hair (keeping a twist tie around the skein). Then I might have to recolour (you have to watch out because if too much brown washes out it gets purple, and if too much black washes out it gets kind of a dirty looking grey-ish colour). Then I root the hair in (I have to put tape all over the face because some residual marker will rub off on my fingers and then transfer to the face if I don't cover it. This did happen with Giselle, so I had to put Oxy-10 on her face, and it came right off).
Currently I am experimenting with some hair that I coloured to see if it sets really well over time.
The one thing I don't know yet is if the "dark roots" will remain stable without fading. I don't *think* it will stain the head, but again, time will tell. I wanted to make sure that the colour was on the *hair* rather than the head, and that I got the colour as permanent as possible before I rooted it around the face.
It's kind of a pain-in-the-*ss method, but so far it's the only thing I've tried that works. But again, we'll have to see over time how it holds up. I know some people have used an acrylic paint wash to do dark roots, but I've
heard it make the hair kind of crunchy and it can't really be brushed after.
I was able to re-boil perm the hair after she was painted and the root colour does seem stable. However, I have to be careful not to touch the top of her hair and then touch the face, as it is quite possible that the ink will still transfer.