Katy Perry has turned her hair blue and I just love it. I think it's bold and beautiful and so Katy Perry. So how do you get blue hair? Well, not that easy, but totally doable, obviously.
First step is to actually remove the color of your natural hair. By removing the color of our natural hair, we give, sort of, a clean slate for the bright colors to show up. So I recommend an all-over color remover, such as Clairol or L'Oreal. I would do an all-over lightener. You follow manufacturer's instructions on how to get the ends and the roots just light enough.
The darker your hair, the more natural color you're going to have to remove. I would say your end result would be a dark, yellowy blond. Once your hair has been all removed to a dark, yellowy blond, it's time to put the blue on.
You can find different products such as, Manic Panic, also in your beauty supply. I think this is a blue pretty close to Katy Perry's.
Once your hair is all blonde, you can apply the product from roots to end, put a shower cap on and let it process for about 30 minutes. One of the tips, when using funky color like this, is never get it on your hands or your clothes or your bathroom because it's not going to come off. And better yet, you could try it at home but I think the best results might be in the hair salon.