I have had my hair dyed red for several years now, fluctuating from a dark dark mahogany red to a brighter "red-red"...I am told constantly by my hairdresser that the only way to color over the red is to go dark. I have no desire to go darker as it will be even harder to get my hair lighter from there. I'm naturally a dirty dish-water blonde with some grays and i would like to eventually get back to a dark blonde shade. I see women do this all the time, and yet i am told that i can't. I have really thick strong long hair and i feel that there must be some way to make this change. Any advice? Thanks.