As going with strange, unnatural colors is typically something done by those in high school or college, age groups where money is typically in short supply, but time is not, it is good to have detailed instructions on doing your own wild colored hair at home.
But for those of you who have some extra spending money, along with the desire for a technicolor appearance, I would highly recommend doing some searching for a salon which will do the color for you, if one is available in your area. Why?
- The primary reason is appearance. While you can surely get even bleaching and even color application yourself, it's a lot easier for someone else to do. They don't have to struggle to see all the way around your head, and they surely have a lot more experience applying bleach and color to hair. If you're going for a multicolor appearance, this is even more important - a decently experienced and skilled stylist/colorist has no problems getting straight streaks, bleaching just the roots, or doing the tips in an even line. A stylist is also a lot less likely to accidentally fry your hair or scalp with too much/too strong bleach.
- You also will get some sort of guarantee with your hair. I've never been to a salon where they wouldn't touch up the cut or color if you get out and about, and realize that something is wrong. If you screw up your own hair, you either have to try again, or go pay someone to fix what you did.
- Time. How Excalibre describes the process, it'll take you at least a full day, if not a full weekend. Go to a salon, and you're looking at a few hours maximum. Eat lunch, get your hair taken care of, and then go off and do other things with your newly colored hair. This occurs without loss of quality - bleachings are nice and light with salon-quality bleach, without taking nearly as long. And with the help of the dryer in the salon, you'll have nice and intense color after about 30-45 minutes, without needing all day. I may just be blessed with hair that holds the dye well, but by the time I had noticable fading, it was time to go get the color redone because of how much my hair had grown out - I never had to touch it up. It looked good right up until the end.
- You don't need to clean up the mess. Sure, you'll still get stained sinks, tubs, towels, and anything else that comes in contact with your wet hair. But that mess is nothing compared to the potential mess while doing the color. When I'm done with mine, my stylist (who's messy, admittedly), usually has brightly colored hands, spots on her shoes (which are already covered in colors from doing just this), has turned 2-3 towels bright colors, and left a bunch of stains on the floor. Myself, I don't need to clean up anything.
- Finally, with a willing and experienced stylist, you can do more unusual color combinations and patterns. Some things are just extremely difficult to do yourself, as you're limited in dexterity and sight when working on your own hair.
I'm not saying don't do it yourself - just remember that, like with many things, having someone experienced and with more resources doing it can yield better and/or faster results. And if you have the means to afford having it done at a salon, you'll likely be happier with the results.
One last note - if you do decide to find a salon, be ready to do a lot of calling around. Most hair salons don't exactly have much demand for unnatural colors, thus don't have anyone who can do it. If and when you find a place that does it well, treasure them, for they are few. Even better is to get a recommendation for a place first - Andromache01 informs me that she had a really bad experience with color at a salon, to the point that she could have done better herself, one handed, in the dark. I'd also check on the brand of dye they use for their color, and I'd recommend Special Effects as the brand of choice for getting vibrant color.