http://whotohate.com/color-lot/
Color Lot
What happens if you add a lot of color to your hair?
Like, okay, say I add blue then green and purple and black [just and ex)] what would happen? And what would happen if I died a lot of it over hair that I would dye totally? Would it fall out or turn to straw at all like some people say? But this question’s a little more specific. Please give a reason for your answer?
Hmm. Not Really a good idea, unless :O you use REALLY healthy/professional dye.
that IS a lot of colours.
i’ve had my hair dyed streaks before; on my bangs, and the bottom layer of my hair.
it was dyed blue and purple. it was okay at first, but then because i had to go through all this process of bleaching and blah blah blah, my hair began to go …bad :S and dry. -it didn’t turn TO straw, but now it is kind close to the colour of straw because of the bleach, and unfortunately, kind of dry like it too :S. but that’s ’cause i was stupid, didn’t take care of my hair properly, and messed with it a lot 
bad decisions.
i didn’t really realize at first, but then as i tried to cover up the bleach with just normal colours such as brown, red, and black, my hair became poorly damaged.
If after you dye your hair; you use good products like colour protection or w.e and proper conditioning often, then you should have no problem.
Hope that helped 
but DO be careful
