All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
We have already clarified in Fataawa 81623 and 88032 that dyeing the hair with a colour other than black is permissible, so please refer to them.
We also clarified the same thing in Fataawa 82802 and 87614 with a condition that there should be no imitation to the non-Muslims or dissolute people.
As regards your statement about a Fatwa issued by a scholar that it is not permissible to dye the hair because the colour is made of chemical ingredients. If the Fatwa suggests that all chemicals are impure, then this Fatwa is not correct. Chemical ingredients are not all impure in themselves to an extent to say that the hair does not become pure. However, if it is confirmed that an impure ingredient is added to a given type of dye, like alcohol for instance, then it is not permissible to use this kind of dye since it has become stained with an impurity.
Moreover, if the dye which one uses forms a coating that prevents water from reaching the hair, then one must remove it, or else, ablution is invalid and thus ritual purity is not achieved.
Allaah Knows best.