I am planning to buy a PM shines 2 oz. to color it on my already colored hair, however, I have a few apprehensions on using it over my colored hair. I have dark brown hair naturally, and I use the same color from Revlon to color my hair to cover the grays. Nevertheless, I want to use PM shines golden blonde color as highlights on my hair, and I am not sure whether it would bring out the best results on the already colored hair. Moreover, I am afraid that the color might turn into a mess, if not come out properly. Can some hair expert please advice whether it would be prudent to use this specific color from PM shines for my colored hair? I would be thankful for an apt response.