The melanin creates a dark colour. As babies age, their melanin level increases and their hair will darken. There are two different kinds of melanin that determine the colour that our hair will become – eumelanin and pheomelanin. Eumelanin determines how dark our hair colour is going to be while the latter determines the warmth of our hair, especially of red heads. The combination of these is determined by our genes which play a huge role in determining the hair colour. Also, it is around adolescence that some genes are triggered by the hormones released during this time and our hair starts changing colour.