good blue hair dye? C:

[baestille]

so, it's november, and that means i must dye my hair another unnatural color. last year i went bright cherry red, but this year i'd like to go blue. i just can't find any good dye. x3 i would use manic panic, but it always washes out extremely fast. this needs to last for awhile, maybe 'til the end of december or longer. :P
click!
i'd like a color close to persian blue or ultramarine on that chart. maybe a bit darker, like navy blue, but s'all good to me.
i have experience dying my own hair. i'm just looking for a good, long-lasting, blue dye. if you know of one, please do tell. thanks in advance! ^^