My hair is light blonde and I have used this product along with L'oreal's Quickblue for doing roots.
The products didn't irritate the scalp at all,after leaving it on for 50 min, it gave a perfect lift of colour.
My hair is naturally dark brown/black, and this lifted the colour to a medium blonde at roots in one bleaching.
Also it works perfect with toner.
I really dislike my hair looking unnatural which means I don't like dark roots and therefor do them every 2 weeks.
This means there is a small level of overlap every time the roots are done, however this product seems to not damage the hair as bad as other products, and I like the subtle change from medium blonde roots to light blonde hair as it grows out.
I find that this product works ideal to create soft highlights or roots.
Would absolutely recommend reading the instructions and doing a test bit just to be on the safe side :) but this product works very well for me.