I dyed my hair darkest brown which turned out to be black, I would like this black to lighten up because I really hate this color on me! I have heard that the shampoo Prell works well for this situation, or using dawn soap with shampoo. My question is how long does this process take, and what do I do if this doesnt fade my color? Thanks!

Prell will work a little bit and it's probably worth a try. It'll fade as much as it's going to within a week -- most of it early in the week.

If it doesn't fade your color, consider ColorFix or Color Oops. You'll have to re-dye after using these products.