The trick to getting blue to stay is:
1. Bleach hair first
2. Leave dye in long enough
-20 minutes to an hour
3. Rinse using ICE cold water
-or as cold as you can stand it.
-I try to wash my hair in cold water for the first week or as long as I can keep it up.
4. Use a color keeper shampoo and conditioner
-not the ones found in drug stores, go to a salon or beauty supply store. I recommend Pearatin or Purology. They’re expensive but totally worth it (even if your hair isn’t colored). I use Pearatin because it has reconstructive properties that my color-damaged hair really needs. If you don’t get one of these at least make sure you find one without sulfate.
5. The last time I got my hair done, it was by a hairdresser friend and she used something after rinsing the dye out that was supposed to keep the color in longer. I have no idea what it was (I’ll find out soon) but it’s amazing at keeping color.
6. I use Punky Color (midnight blue) but I’ve heard great things about Special FX.

One more thing… to avoid getting blue everywhere, use gloves and put vaseline around your hairline.