I want to dye my hair a green because I want it. I like the colour not because of other people. Am I allowed?
If Allah wanted to there would have been hair colors of pink , blue or whatever but every skin tone has a complementary hair color and eye color and so on . It is part of Islam to respect your body and not to mistreat it because you will be questioned for its well being. You are allowed to enhance the beauty Allah has granted you with but to change entirely is something you should decide for yourself.