Recently, I've been getting my hair professionally colored at a (pricey) salon where they use a new L'oreal professional hair color that's ammonia free -here's some info on it: http://www.stylelist.com/2010/01/28/l-oreal-professionnel-ammonia-free-hair-color/ My hair is dark brown/almost black so I do a single process color to keep it similar to my natural color. The problem is, it doesn't fully cover the few pesky grays (they're actually white not gray) that I have...it gets some but not others. Plus, it only lasts a week for the ones it does cover. (Btw, I use a sulfate-free shampoo for color treated hair). I haven't had a chance to discuss it with my stylist, but I'm just wondering if anybody knows of anything that I can use prior to coloring to help the color adhere to the grays. I like that my hair feels natural and healthy after this color, but it really isn't worth it if it won't cover grays. Any and all advice is appreciated.