I color regularly, I have 4a hair and I use commercial, permanenet dye I mix myself and have not had any problems, especially since no longer relaxing.
My hair is dark brown but I lift to a medium auburn color.
I pre-treat before I color, I deep treat after the process is over (protein and moisture), and I deep treat once weekly. If you want permanent grey coverage I recommend the permanent route because it seems more predictable than other methods (for me).
I color my own hair but I recommend people let a stylist do the color if they don't feel confident enough. Unless you are very experienced, it is hard to anticipate how fast the color will process, what kind of developer you need, etc and how to correct if something doesn't turn out as you expected.
Fine strands, not as densely-placed as I would like
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