I used Wella Renew and I am not entirely sold on it. The first time I used it was on my own hair. I had used 9/61 as I always do, but for some reason the tone grabbed more and I got a lot of lavender (like) over depositing. I think it was because I had just come back from 2 weeks in Mexico and my hair was butchered from sun and chlorine. Anyway, I had bought the Colour Renew about a month earlier and had wanted a chance to use it. In fairness, it did get all the tone out of the hair and set me back to a light brassy blonde. So on the first round, I was impressed. I found it quite runny and somewhat tricky to apply (as it dripped) but it did do what it promised it would.
Second use (however) was a different story. My daughter's friend had applied a box colour and rather than the chocolate she had hoped for, she ended up with a black! (Usual story!). I used the Wella Renew and put her under heat, but after 45 minutes it ultimately was not budging that much. I gave her a second application (again) under heat. This time it got her from a black to a soft darker brown and she was not actually that unhappy as it was better than the black. But I don't think you could call this a colour remover as such.