Bleaching a crew neck sweater

So I have this blue crew neck sweater (http://i.imgur.com/mz2OHy2.jpg) and I want to bleach it because the color doesn't go with my wardrobe at all.

The sweater is 68% polyester and 32% cotton. Is it okay to bleach it or will the synthetic fiber get burned? My google searchs have given me mixed results. Some people say its okay, other say that the color wont be removed from polyester.

Also, what proportions of bleach should I use? 1/3? 1/4?

Thanks in advance!