My hair is medium brown right now. How many bleaches should it take to make my hair light enough to take up a vibrant blue color?

If you get it done at a salon, they only have to bleach it once.
I got a vibrant pink color in my hair yesterday and I didn't have to wait too long for the bleach to make my hair light, and my hair is darker than your's.

Blue?

uh...i'd forget about the bleach; if you have a reasonable amount of red tones in your hair (most brunettes do) bleaching will turn it orange and i don't know how well blue would cover orange.

the are brands of hair color that'll show up over dark hair. i think a brand called xtreme does. take a look at your local drug store.

if you're going to go the bleach route, have it done professionaly. trust me, i've bleached my own hair and oh what a mess that was!

lol. my friend just dyed her hair blue. actually the whole softball team did it. lol Yay school spirit!

I know... pointless comment.

If its reddey brown it'll go orange. But another bleach on top usually sorts it out. But I'd wait a week or two though... so your hair doesn't fall out or anything

Its really just easier to go to a salon

Unless you're going dark, go to a salon...
Trust me, I've been tring to get it really blonde for years...
Then I went and they got it Marylin Monroe white in one sitting...

I had dyed black hair, and one bleach was enough to get it light enough to go a bright blue (see my avatar)

I bleached it myself, and it did go fairly orange, but the blue covered it.

i had the same color as you.

it turned a funky orangey color, but then they dyed it a blonde color.
so i'm thinking blue would cover it up.
get it professionally done though.

i got my hair died blue a few years ago, was only bleached once if i remember rightly, my hair is a medium to dark brown, bleach is quite strong, i always assumed you only needed to do it once, i might be wrong, i'm dying my hair blue again today funnily enough, tho goin for dark blue this time so not botherin with the bleach.. problem i had last time was the blue gradually faded and left the bleached hair a sort of greyish colour for a week or so...

Also depends what brand you're using.. as to how well it might cover any orangeness.
If its orangey to start with the blue might cover it initially but if it fades, it goes a lovely sort of sewage colour... But I doubt it will take it more than 2 lots of bleach to get it white

My friend has blue at the moment, and it took 2 lots of bleach to get the scary metallic black dye out. Though shes trying new dye, and it doesn't look like it stuck very well, its fading without her washing it.. =/