Have you had other reasons as well? Such as doing it to cover white or gray hair? Or perhaps change it due to fashion?
I wish I was more adventurous with my hair, but all I've done so far is use dye to cover grays.  That's the reason many people use hair dye.
I just dyed my hair light purple. I am really excited about it! Neat, hair coloring can be done at home or by a hairdresser, which way did you go? I went to a hairdresser to have it done. Cool, the Celtic people was described by Diodorus Siculus, a Greek Historian, to have dyed their hair blonde. That's really cool! How did they manage that? They bleached it through washing it in lime. Then they comb it back from their foreheads. I guess people have always wanted to try different things. That is super interesting!
The main reasons for this are cosmetic: to cover gray or white hair, to change to a color regarded as more fashionable or desirable, to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching.