I color my hair because it is beginning to turn gray. I've dyed my hair various colors through the years but now I just want to cover the gray with a light brown. I decided to try Clarol Natural Instincts - 6 light mahogany brown. It covered the gray but the color is a much darker brown than I would have liked. I realize now I should have tried a lighter color, maybe a 7 or 8. How would you recommend lightening the hair?

I should mention that I went to a hairdresser as the roots grew out but she said I didn't have a choice, because she recommended against lightening all of my shoulder length hair. She treated the roots with what she said was a slightly lighter formula that can gradually take over but it looks just the same. What process should I now ask for when I go to a different hairdresser? Overall I just want a light brown that is a shade or two lighter that what I currently have.