The color isn’t the same as on the box
It rarely is. Haircolor is supposed to work with your own haircolor (natural or otherwise – basically whatever you have 
right now) to produce something approaching a natural enhancement or at least individual, color. Unless you strip your hair to a pale blonde, the color on the box is usually never the same color as what you wind up with. No need to panic, just figure out what about the color is wrong; if it is too dark, try washing it a few times to see if it lightens a bit; or strip your hair and apply a lighter shade in the same color family. If it is too light, go one darker. Not red enough get a redder shade. It’s pretty simple.
I want to take this color out of my hair
I have had reports that using dishwashing liquid like Dawn or whatever can help rinse out demis – this applies to semi-permanents as well. Try it if you want to, I haven’t tried it, so I can’t say if it really works on me. What has worked is a product called “UnColor”. It comes in an aqua blue/turquoise colored bottle and is designed JUST for removing semi-permanent haircolor. There is also an “UnColor” product for removing permanent colors from hair, but I have never tried it.
In any case, removing that color isn’t going to be fun. You might, if the color is permanent, have to strip your hair. This is an involved process better done by a pro (or your Aunt Jane if have a helpful aunt type around). It involves degrees in art and chemistry and requires patience and a sense of humor – very rarely will blue-black hair dye come out in the first stripping, if at all (I speak from experience there). You will probably have blonde roots and purple rest-of-hair for a while between times of stripping (you can’t just strip your hair nine times in one day. You could, but I don’t advise it. At ALL.)
If the color is demi-permanent, washing it a hundred times won’t do the trick either. Most demis have peroxide in them, which means your hair is slightly, but forever, altered. Most of it will wash out; not all. And on light blonde hair, it sometimes never washes out. That is the chance you take.
Semi-permanents, like Loving Care, 99% of the time, wash completely out within a week or so (at least amongst my friends and I). Unless you have bleached your hair very blonde and put black Loving Care on your hair, if you are just using it on virgin hair, it will wash out. If you are putting it on bleached hair and it is refusing to budge, you will have to bleach it out again, unless your stylist has a better suggestion. (This is why there is a whole field called corrective coloring, folks.)
The hairdye turned my hair green
Woops! This was probably because the color you chose had a green undertone to it. Hair color works on the color wheel. All hair colors have undertones to them. Some browns and black have green undertones. In the future, try using a color with a blue or purple undertone to it. You can usually get the undertone information right off the bottle if you buy your color at a beauty supply store, but if you are unsure you might call the manufacturere and ask them. My only other suggestion is to either bleach it out or cover it up. If you don’t panic, you might call a pro and ask what to do – although they usually just tell you to make an appointment and come in so they can charge out your ass to look at your hair for 5 minutes. Anyway, those are your choices. Bleach it blonde or dye it brown, red or black, just choose a color and try again, as long as your hair is in good enough shape for it.
The hairdye turned my hair orange
If it was supposed to be blonde and came out orange instead, then your hair is probably too dark for single process blonding. You will have to purchase bleaching supplies and bleach your hair and then add a toner (double-processing) which is sorta involved if you arent really into hair dying. If you dont want the trouble, go to a salon, or give up on being blonde.
If you actually got to a light blonde but there is just a little brassiness in it, they sell this stuff called “Drabber” at beauty supply stores that gets rid of brassiness and orange/gold tones in blonde hair, you might check it out and see if that’s what you need. Another alternative would be to try one of the purple-undertoned shampoos like ARTec for ash blonde or Clairol Compliments in ash blonde which worked for me in eliminating unwanted brassy undertones.
My hair isn’t blonde enough yet and I need it done by tonite
You can either take the chance and bleach it again, cancel your plans for the evening and stay home to wait for 24 hours to pass so you can bleach again, or call it a failure and pump some brown on it and go out.
I bleached my hair and used Manic Panic and it isn’t washing out
Manic Panic after Bleaching/stripping your hair is pretty much permanent, or might as well be. You can wait it out if 
youre the patient type, but my friend Jeniffer waited six months and the stuff never came out. It got to a real weird pale blue and just stopped rinsing out. She gave up and just let it grow out and started over rather than bleach that blue out of her hair. Those are your options; as always, bleach it again to get it out (good luck – although I accomplished it with much pain) or dye over it with a color that will cover it (not golden blonde, it will have to be black or brown to cover most Manic Panic shades).
I bleached my hair and it is all different colors
Didn’t I tell you to get some help? You better get help this time. Get someone and mix the stuff and have them go over the splotches, leave the mix on till it matches your hair, then rinse.