If you aren't pleased with the way your hair colour turned out, there are several ways to deal with your dissatisfaction. If a professional coloured your hair, go back to her and ask what you should do. Your hair stylist will best understand how to fix your hair.
If, on the other hand, you or a friend coloured your hair at home, then your situation is trickier. You can seek professional help, or you can call the manufacturer or visit a local beauty supply store and ask for advice. The best course of action will depend on your hair and how different the colour you have is from the colour you desire.
Seek professional help. Whether your stylist coloured your hair originally or not, don't be embarrassed or shy about seeking help from a colouring specialist. Try to find someone whose focus is colour. Ask for recommendations from friends, look at online ratings like Yelp!, or ask your Facebook comrades if they know any local hair colour maestros.
Often overly light hair can be darkened up with toner. Toner doesn't damage hair the way dying does, so if that's all you need, there's nothing to fret about. Toner is designed to gently change colour slightly and won't take you more than one shade from the colour you have, but it will tone down brassy hair by getting rid of hints of red, yellow or gold. Ask a professional what toner to use for your particular dilemma; there are different toners for different issues.
If your hair is more than one shade too light, you'll probably need another dying session. Definitely seek professional help with this. Dying hair repeatedly causes damage, including breakage. You may be able to take your hair to the next colour level with a temporary or semi-permanent dye, which are less harsh than permanent colour.
Put on a hat. If you can't bear to have your hair viewed by the scornful eyes of others, wrap your head in a pretty scarf or dig your favourite hat out of the closet. If you don't own either, treat yourself to something new. Hats and scarves will hide your little mistake until you are able to get a more permanent fix.
Try some new hair styles. Maybe you can find one that works with your light colour. Or, check out hair powder products now on the market. Check out The All Nighter or Bumble and Bumble Hair Powder. Henna is another alternative. If the solution you decide on will permanently deposit colour on your porous light hair, get the input of a professional.
Look for the humour in the situation. It feels awful when your hair doesn't look great, but freaking out isn't productive. Do something zany like style your super light locks in a funky up-do and have a friend take silly pictures of you before you get your colour corrected. Have some fun with it. It's just hair, and taking a humorous approach will make you and those involved more at ease.