I'd think you'd have to wait at least a few days (if not weeks) to let you hair rest before anything else is done with it.
Maybe you could try something different. You can get a very nice brown color by using henna and indigo.
Here is the 'easy brunette':
http://www.hennaforhair.com/mixes/katharineg
Other colors and how to get them are here:
http://www.hennaforhair.com/mixes
My original color is brown but some gray is creeping in.
I started using henna 5 years ago, and I get a chestnut auburn color with the gray becoming coppery highlights.
My hair is not fried from all kinds of chemicals, I have no spilt ends and I'm growing it longer now than I ever could before (past bra strap).
The forum at the Henna for Hair site is very helpful, and they are very good about answering questions. It might be more than what you want to try, but it's nice to know there are other ways to get a nice hair color.