Q) I've just died my hair black today and I want red highlights. How long do I need to wait to add them?
Professional Hair Care Answer - If your hair is generally healthy, it won't hurt to add the red highlights very soon. At least wait until you don't see any black hair color coming out of your hair when you shower and shampoo though. Dark colors have very large quantities of color molecules and they take a bit longer to adhere to your hair.
If your hair is not in good condition, I would still wait a few days. Either way, just condition it well and wash it one more time before you add red. Black hair colors seem to wash out a bit more in the second, third, or fourth shampooing, and that will help establish better color when you add the highlights. The hair strand is full of black color right now and can't absorb much color without losing some first. (called oversaturation) I would suggest using a clarifying shampoo like Nexxus Clarifying Shampoo once or twice to help speed up the process if you like. But don't speed it up so much that you stress your hair or damage it. Clarifying shampoos can be terribly harsh on your hair.
Have you highlighted in red before with a black color on your hair before?
You will need to 'lift' your hair, since you can't add color to black without doing so. You will need a stronger peroxide than the color in the box provides, if thats what you're planning to use. You may get some lift out of the regular box color, but it won't be much. You can get all the color help you need if you buy my hair care and hair color ebook.
And remember, giving me details enables me to give you the best advice possible! I will tell you this though. If you want red highlights, really just about any lighter color will give you some red. Black hair can only go up the color scale and red is the next color it will turn. So you see, you can probably get red hair color by using a light brown color. Just stay away from ash browns because they cancel out reds instead and can look drab.