Dumbest Hair Mistake Evar?

[Ace]

Bleaching is a fine art, esp. when there's pre-existing color in the hair. You have to do a split aplication, first to the hairshaft and then when the shaft has reached two shades from desired lightness apply with a lower volume developer to the roots. You also want the hair foiled so that it incubates the bleach and prevents runnoff from the chemical reaction that happens when bleach and the mordants in cheep dye mix. Blue is one of those shades that's hard to get unless the hair is virgin before bleaching because most dyes will leave an orange psudo-melanin that bleach doesn't break up well. That orange mixes with the transparent blue stain-dye and makes a muddy greenish color (if your lucky) or the two will cancel each other out and give you an ugly flat brown.
You can probably get away with bleaching it again (don't bleach the roots!) and then coloring it followed by a PROFESSIONAL deep condition preferably at a salon that uses Bumble and Bumble, Enjoy, Pureology, or Redken products. Otherwise your hair will feel like shit and the color wont stay. It'll still be damaged and you'll have to get a top notch conditioner for home use and a leave in conditioner to make combing it easier. Also a wide tooth professional quality plastic brissle denman brush will make the comb through easier.

Or you could go see a local hair guru and have them work their magic. It'll cost more dollars but it'll save your hair and sanity.

Ah, this photo is weeks upon weeks old! I got away with dying it blue (using manic panic) which stayed lovely for a couple weeks, and then I went dark brown, which my hair has stayed with no nasty surprises since the bleaching incident. My hair was quite damaged, but I cut off about 3 inches and its been good since! I put it through so much, and my hair remains faithful to me

[Syrran]

Ah, this photo is weeks upon weeks old! I got away with dying it blue (using manic panic) which stayed lovely for a couple weeks, and then I went dark brown, which my hair has stayed with no nasty surprises since the bleaching incident. My hair was quite damaged, but I cut off about 3 inches and its been good since! I put it through so much, and my hair remains faithful to me

Well you're gorgeous either way.

[Dusk]

Lets see... I dyed my hair dark blue but you could only tell in strong light otherwise it looked black, at the moment my hair is about 6 mm long cos I gat a trim before a job interveiw.
but the worst would be summer almost 3 years ago, i had my hair shaved a bit longer than it is now and I decided I wanted crimson hair, but when I put the stuff in my scalp turned blood red and my hair went from blonde to pink and it was supposed to wash out but it stayed in for almost 4 months.