i'm so in love with the schwarzkopf brights range. they're affordable, provide great color (granted that the hair is lightened to the recommended shade) and for me, they last a heck of a long time.
i recently found this in my local supermarket, and i actually did a kevin from Home Alone, only my face was of pure elation and not because i'd just shaved and covered my face with aftershave. i threw two boxes in my cart and away i went, happier than a pig in mud.
i wasn't expecting this to work so well, as i was trying to cover up orange and pink, colors that have been in my hair for more than a year. when color has been in that long, or at least reapplied over and over again for that long, it tends to grab the hair and it doesn't want to let go. the pink i didn't have much of an issue covering, but the orange, yes.
from the middle of the hair to the tips, it's a gorgeous bluey color. i wouldn't call it turquoise myself, i feel it needs more green to be called turquoise. but it is a really nice blue color that's not too dark and not too light. it is perfect. it didn't cover the orange too well, but it also didn't merge with the orange to make a horrible color. with a few more dedicated touch ups every month i think it'll be covered perfectly.
i foresee this lasting a decent amount of time, simply because blue is a very hard dye to remove from the hair and i think it'll fade really nicely. i'll definitely be using it again, and i have already bought a few backups!