Normally Manic Panic hair colors don't last in my hair at all and normally starts fading after the first wash. When I bought this color and put it in my hair after my Rock N Roll red dye faded, I dyed my hair Voodoo Blue and it was beautiful teal color even on top of those colors (so no you don't have to bleach your hair a pale yellow). It lasted an extremely long time too. I think I had it in my hair for at least two months before trying to change it cause I got bored with it. A little while later I dyed my mohawk black, and left the sides bleached, but some of the black got into the bleached sides because I wasn't careful. So I experimented and put the voodoo blue ontop of the greyish hair and it obviously had a darker value, but completely covered all of the mistakes I had in the sides and you couldn't even notice. I don't know what MP did, but they definitely changed their formula for this color and I hear the other new color Rockabilly Blue is a great color too (but it's heavy and you have to use a little at a time).
This is the best MP color I have ever used.