Food colouring can safely be used as a hair dye for colouring your hair. It is semi-permanent and usually takes two to four weeks to completely wash out of your hair. The longer you leave the food colouring in, the darker the colour of your hair, and the longer it lasts. Colours show up better on lighter hair than darker.
Mix several drops of food colouring and a couple tablespoons of shampoo in an empty shampoo bottle. The more food colouring you use, the darker the shade of colour created. Put the top on the bottle, and shake it well to mix. You can add a couple of drops of water if it seems to thick.
Wet your hair thoroughly, and then massage the food colouring and shampoo through your hair. Be sure to cover your entire head of hair evenly if you are trying to dye your whole head. You can also separate segments of your hair and dye only part of it.
Leave the food colouring in your hair for six to 12 hours. If you have blond or light brown hair, six hours is probably enough. If your hair is dark brown or black, leave it longer.
Jump into the shower, and rinse out the coloured shampoo. Towel dry your hair, and then dry it with a blow dryer, or let it dry naturally.
Avoid washing your hair for three to five days. After that, you can wash it as you normally would, but each time that you wash it, the colour lightens. Depending on how dark you dyed it, the food colouring completely washes out within a month.
Wear old clothes, and be careful where you sit while dying your hair with food colouring. Any shampoo and dye that drips out of your hair also dyes whatever it drips onto. You can also dye your hair the same way, using gelatin or drink mixes. If you choose to use one of them instead of food colouring, be sure to pick a product that either has no sweetener in it, or is artificially sweetened.