Make sure your hair is white

Pretty expensive dye in my opinion. I tired this colour on my pre-lightened blonde hair and I was going for a purple/grey look. I'm no rookie to hair dye so test strand that first! The color was gorgeous for about 1 day (I almost did my whole head after that) but faded on my first wash to a HORRIBLE green. I guess my underlying colour was too yellow and pulled too much blue from the dye, but it was pretty pathetic considering it advertised to last for several washes.