This color last forever like no other (it won't come out even if you bleach it over)... I dyed my hair 4 months ago and my hair is still green, it has only faded a bit in some parts, from a green-blue to a pine-green.
This color changes a lot depending on the color of your hair, over bleached white hair this color is blue, and over bleached blond/dark blond this color is green (my real hair is black, so I had to bleach it a lot).