Although hair color is dependant on dominant and recessive qualities, predicting hair color is more complex than predicting other genetic traits. Rather than one or the other, hair color is additive, meaning the pigment melanin along with a variety of genes determines how dark your hair will be.
Melanin
There are two kinds of melanin, eumelanin and phomelanin. A combination of these two is what determines the exact color of your hair.
Function
Hair color is determined by a number of genes. These genes determine the amount of eumelanin overall. The more eumelanin you have, the darker the hair color will be.
Dominant Hair Colors
Dark hair is dominant over blonde and light hair. Non-red hair colors such as blonde and brunette take precedence over red hair.
Recessive Hair Colors
Recessive hair colors include blonde hair, light hair, and red hair. This also means that although blonde hair is dominant over red hair, it is recessive to dark hair.
Other Factors
Because hair color is more dependant on the pigment melanin, it also subject to changes in the body. Infants have less melanin than adults, so they may have lighter hair color. Environmental factors like sunlight may also change it.