Dying chemically processed hair can be tricky. Timing is important to avoid over-processing and damaging the hair. I use a texturizer (a mild relaxer) in my hair and I always wait two weeks or more in between the processes. Many African-Americans have thick hair so thoroughly dying the roots can be a challenge, but I have developed a technique to make the process a breeze.
When it’s time to touch up your roots, you can clearly see the difference in color so you know where to put the dye. First wash your hair to get rid of any hair products that have built up then dry your hair thoroughly. The dye will not take if your hair is dirty or damp.
Part your hair down the middle then section it off into several ponytails forming a grid across your head. This way you will be able to see where you need to apply the dye. Going from front to back, go through each part and saturate roots with dye. Next rub the dye through roots with your gloved fingers to make sure it has penetrated the hair. Be as careful as possible to not let the dye overlap previously dyed hair. This can ruin the color of the hair that has already been dyed and it can also damage it. There will be a bit of overlap, but keep it to a minimum. Use a handheld mirror to check the back and top of your head to make sure you covered all the parts.
After you have dyed your roots in the parts, undo ponytails one by one and continue dying the roots, rubbing the color in thoroughly. Metal clips are helpful during this step to separate the loose sections as you go through them. Continue using the handheld mirror to check the progress of you color. Rinse when you have achieved the desired color then condition and style as usual.
Now that you have the desired hair texture and color, it should be several weeks before you start seeing new growth again. At that point you can decide which process you want to do first, relaxer/texturizer or dye. For me, it depends on the time of year, my mood, or my schedule to determine which one I want to do first, but it may be easier for some people just to keep a set regimen of process then color or vice versa.
This technique for dying your hair can be used for chemically processing hair to avoid damage and remember to always use conditioner after each process. Chemically processing and dying hair can be hard on the hair if not done correctly, but if you stick to a set timeframe in between processes, your hair should turn out just fine.