Most of the hair dyes contains animal byproducts, which could be haram. And even if you find one which contains synthetic material, you will have to check with the company whether that dye will just color the hair or it will perform a coat on top of a hair. If it will just color, then you are allowed to use it, but if it will be a coat then your Ghusl will not be completed. That is why it is better to use Hina to color hair.
And Allah knows best.
Ask Alimah Team
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