I want to go back to my normal hair color

So about two or three weeks ago, I colored my hair black, permenant.  I love the color and it looks really good and everything, but I just think it's going to be too much of a hastle to keep coloring it all the time.  My natural color is light brown, so I get kind of bad roots.  Anyway, I was wondering if I could go back to my normal hair color, without getting my hair bleached, and without waiting for it to grow out.  Would it be possible to maybe get my hair colored a lighter and lighter shade, every two - 3 weeks, until I am back to normal?  Thanks for the help guys, and I apologize if this question was posted already.  Maybe someone can forward me to a previous topic that deals with this problem?  Thanks again :D