I use this with L'Oréal Majirel dyes on my hair.
I had bleached hair that was dyed blue, and was ready to go back brown. I tested it on my hair and it worked well even without an in between colour. I dyed my hair red first anyway, then put Majirel on top.
The dye continues to rinse out for a few showers, even after the water runs clear, there will be more next time. After about 15+ washes my hair is a nice colour and I'm happy with it, the colour lightens and begins to suit my hair more naturally and matches my roots.
I noticed later, a small patch that is still blue, I don't think this is because the dye rinses out, I think it's due to being in a tough spot to see. I just never noticed I'd missed it until now. I went over it with Majirel again, it was a bit darker than the rest, but came to blend nicely.
Good product for roots, grey hairs, and simply all over head. Fantastic value- I have too much left! Since I only need ~ 100ml per tube of Majirel. Will last forever!