I've been looking everywhere for white hair dye, but the closest I've found is white toner and some spray-on temporary metallic color. How well does this work? Does my hair need to be bleached very light for it to work properly? Does white or grey hair dye even exist?

I'm looking for something permenant or semi-permenant. Also, is it bad that I've bleached my hair twice and had the roots retouched once in the past year? I really want my hair to be as close to white (or grey) as possible, but I don't want it if it means all my hair will end up in the bathtub drain. How much can my hair take? I had my hair bleached probably 4-5 months ago, which was about 3 months after I bleached it the first time. My roots have come back quite a bit since they were retouched (which was probably 4 months ago). Is it safe to bleach again? My hairdresser advised me not to put anything in my hair for a while after she touched up the roots because it was so damaged. But I don't know how long "a long time" is to her.

Unlike the first two bleachings, I may actually go to a salon rather than leave it up to my roommates. Would my hair fall out or break off if I were to have it bleached white?

I know I have lots of questions, but I just don't want to risk having my hair fall out. I'll just sum up my entire post in one question: How can I make my hair permenantly or semi-permenantly white or grey?