R.J.
I used to use manic panic ... full rainbow spectrum - Red to Purple & everything in between all the time. My favorite for my coloring was cherry blossom pink and lavender. I'll still occasionally add streaks, just for fun. But I can also get away with it since I'm married to a musician ;)
Here's the plain truth: if you don't bleach your hair, it won't come out colored correctly. Blue violet on dark hair will come out shiny blackish with bule/purple highlights.
Tip 00 : GET YOUR PARENTS OKAY. Trust me. OTW, they'll just make you dye it back, and it will be lousy/ pointless.
Tip 1 : YES, you have to bleach your hair unless you happen to be light blonde.
Tip 2 : Start out with a SINGLE strand, and do it up frontish or on the sides where you can see it, but not top hair. Pick the strand, about the width of your finger. Rubber band it. Now tie up the rest of your hair. Bleach that strand according to instruction. Then add the manic panic according to instruction. Once you get an idea about how long you have to leave it on to get the color you want, you can do multiple sections at a time. BUT IT ALWAYS LOOKS BETTER to be adding more sections slowly, then to do a whole bunch at once.
Tip 3: IT IS WORTH IT TO HAVE IT PROFESSIONALLY DONE if you want more than colorful highlights (as in all over color). Very few salons will do "rocker" or "punk" coloring. It is 100% worth your time and money to do so. Otherwise you can end up with half melted, fried, or "straw" like hair, and the color will be very, um, variable.
Tip 4: Certain colors last longer. Reds and blues last the SHORTEST amount of time (because the color molecules are smaller and wash out of the strands the fastest) and black lasts the longest (it's almost impossible to remove black hair dye... it comes out a mottled orangey black mess if you try) because black has the fattest molecule. There are certain things you can do to have the color last longer. NO GLYCERINE in your conditioner is #1. Nearly all conditioners have glycerine. The only ones that don't tend to be the ones specifically made for color treated hair. #2 be prepared to retouch your hair on a regular basis. With certain blues and fire engine red that can mean on a weekly, or every other week basis. You don't have to rebleach your hair, just add more of the pigment.
Tip 5 : Vaseline & Showercaps. When you're adding streaks to your hair, take the ponytails of the to be streaked areas and poke them through holes of a cheap shower cap. You'll look ridiculous. BUT it keeps the rest of your hair from getting splashing, spotted, and dripped on. Vaseline is for the line of your face around your hairline. Very little looks stupider than if you dye a portion of your face or neck on accident. Separate out the strands. Poke them through the shower cap. Tuck in any "esacpe" hairs. Take vaseline and wipe about a 1" line all the way around the edge of the showercap / along your hairline on your *face & neck* (not in your hair)
Tip 6 : They dye will stain towels. If you don't want to get yelled at.. make sure you're using old, raggish towels.
Tip 7 : If you're doing ANY areas near your eyes (bangs, etc.) wear swim goggles. You'll look even stupider as you are in the process of dying your hair, but they keep you from going blind if you get any drips in your eyes.