I died my hair black, from Mahogany. I don't like it, how soon can I die over it? Should I use a lighter color rinse over it?

If your hair is in good condition you may dye it right away. Hair color rinses only deposit hair color onto hair and will last around 6 shampoos. It will not make your hair lighter. Some permanent hair colors with a 20 volume peroxide developer can lighten the hair 1 to 2 shades, however, it could turn your hair red/orange since your hair is dark. If you want to go more than 3 shades lighter, you will need to bleach and then apply your desired color.