I can understand warning people about bleaching or colouring their own hair, given the amount of posts I've seen pop up on this forum about such things going wrong. Even if you don't end up seriously damaging your hair, you can end up with it lightening to a horrible colour.
I have thick coarse arse length black hair, and I've bleached and coloured it numerous times without issue, even having bleached my hair out to platinum blonde on several occasions without doing serious damage. So, I think it's completely possible to do your hair yourself without destroying it, however, I think that it takes a certain level of awareness about your own hair that most people don't have. This is not to be rude about what people know about their own hair, this is about the fact that hair dressers are trained and experienced professionals who should be able to assess your hair and choose a course of action that will work for your individual situation. As an example, most people look at my hair and see jet black, but a good hair dresser should see black with a very distinctive red undertone. That red undertone makes a huge difference in the way bleach will react on my hair, if I was simply to straight bleach my hair it would turn a brass colour rather than blonde, but if I bleach and then colour with a light caramel wash it counteracts this and leaves my hair a gorgeous natural looking golden blond. For the record, yes, this is in fact a technique a hairdresser taught me. Because your hair's coloured it's not simply about your natural colour, it's about how the dye that's already in it will react along with that natural colour.
If you're not confident in doing it yourself, I would highly suggest simply saving up to go to your friend. Personally, I think paying for peace of mind is worth it.
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