Main reasons other than fashion would be hiding gray or white hair and restoring one's original hair color.
Thank goodness for small favors!  LOL Why did you want to color it?  For cosmetic reasons, to cover gray?
I just dyed my hair burgandy, kind of regretting it Oh wow!  Did you have it done  professionally by a hairdresser or did you do it yourself at home? I did it at home and obviously did not think it through, Burgandy is not a natural hair color so it looks weird Sounds unfortunate, although home coloring got 1.9 billion in the US back in 2011. Why is there so much hair coloring sales anyway? I understand it to be for fashion since that's what I tried but other than that I don't get it.
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.