Lol there are a lot of stylists on here. I am not one of them. I am a home colorer through and through. One thing that helped me even out the color when I did this was to use a protein filler on the hair, both a treatment after lightening/before coloring as well as an additive to the hair color mix (you can find it at a beauty supply store.) You should probably chill a minute before putting your hair through anything else, use some restructurizing conditioners and whathaveyou. What shade of red are you going for? Now that you've used brown, you can't go any lighter than that brown without lifting again, and I fear that would turn your hair to linen cloth. If you are using semi-perm color, the red will kind of be a wash over the brown. Theres a good chance your roots will be lighter, unless you color match with a brown and just do your roots as though the lighter color were your natural shade and you wanted to do your roots to match the brown you've put in your hair. As your hair grows, the change from the processed hair to the more "virgin hair" will be less noticeable. If you have a short do, it can be really punky to have, say, bright orange roots, and red tips >:-) At any rate, good luck!