I bleached my hair from black to white with yellowish tones in the end of my hair. I ordered two tubes of manic panic voodoo blue from eBay for £21.50 free p&p. (I bought two because I wasn't sure how much I would need.) I applied the hair colour to my hair and over saturated it, I also had enough to do my 20inch extensions with just 1 tub which I was pretty impressed with because the consistency of the formula was very creamy and felt good on my hair. I left the hair dye on my hair and extensions for an hour and thirty minutes and then rinsed with cold water. The colour was very vibrant and was many shades of rich turquoise blues and dark greens. It stayed in we'll for the first three washes and still looked pretty good but then for me the product started to slip. A lot more started washing out than normal and the colour faded quite unexpectedly, my hair has turned bubble gum/light blue on the top and a mint green on the ends which is not to my liking. I would recommend not buying this product if you are not willing to pay a lot of money to keep topping up your hair dye. But if you are then top up on them because you are going to need them. Also try and get your hair as light as possible as it will turn a dark green even if the hair is slightly yellow.
Voodoo blue lasted ad stayed vibrant in my hair for awhile, an when it did start fading (as all dyes have to do) it faded evenly! Most dyes fade in patches but oh not voodoo blue! It just looked like i was a lighter blue not like i didnt take care of my hair of anything.
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.