looking to blend my greys in with a light brown semi permanent colour- the rest of my hair is dark brown, semi has no ammonia or peroxide, do you think this will work? Does anyone do this? I’d like to make the greys look a bit lighter than my natural colour but worried it will do funny stuff to my existing natural brown; what do you think? Note: existing brown has reddish tone which I’ve spent fortunes trying to get rid of!