What causes different skin colours?

It you walk down a street in any town or city, you will see lots of people with different coloured skin: white, black, yellow and coffee colours all appear. But why do people have different coloured skin?

The reason is that in your skin you have substances which, under certain conditions and with the correct chemical processes, make colour – the different shades of human skin. The amount of each different colour or chromogen in your skin determines what colour you are. One of these colour is formed by a substance called melanin, which appears as black or dark brown when it comes into contact with sunlight, and which gives you a sun tan. Everyone has melanin in their skin, but people who live in colder areas. It protects them against the harmful rays of the sun. other colours in the skin are yellow, which is caused by a similar process as black; red, which is caused by the presence of blood vessels in the skin, and white, which is the colour of skin without any colour in it. The balance of these four colours in your skin decides what colour you are.