If you have dark colored hair and want permanent gray hair, you should definitely open the hair color. Your hair will have to open up to the extreme edge that can be opened. Of course if you use light yellow hair color in the present, your job will be much easier. You have to find the least harmful of the openers used at this point.
It is also an important hair coloring technique that adds a dimension to the hair that leaves the hair darker. But it is imperative that you do it correctly. It is not even if you look otherwise neglected! When you are coloring your hair shaft at home, start from the front of the hairline and move backwards.