Light is made by photons having different wavelengths. Each wavelenght in the visible spectrum is associated, by our brain to a color. When photons of each visible wavelength are mixed toghether we perceive the light to be white.
When this white ray hit a surface part of the wavelength will be absorbed, while other will be reflected depending from the material of the surface. The mix of the reflected wavelengths will be then perceived as a color. If all the wavelengths are absorbed we will percive black, that is no ligth.