i always do my hair myself, or with my sister, but the last time i had a voucher so went to the hair dresser and she was like, if you go blonde to brown you have to strip it first because otherwise the colour won't stay. and when i think about it that's true, it has happened to me, but if it bothers you then you just buy another packet of hairdye and you're still better off than hairdressers.
except if you are unco like me, and mess black hair dye down yr sister's neck/forehead so her face hairs/neck hairs were black. so i was like ooh must wax, but she was like no way, so just got all chemicals out of the garage and attempted to remove dye. and then put the cloth she'd used in the washingmachine with my mum's bedsheets. hairdye excitement