Indeed it is. There are two different types of cells responsible for visual stimulus. "Rods", as they are known, are responsible for differences in light intensity while "cones" are responsible for colour differential. Colour blind people don't necessarily have less eye cells overall, but rather a deficiency of cone cells. The totality of cells is comparable to a normal sighted person and the lack of cones is made up by rods, which in turn can cause an increase in light sensitivity for colourblind individuals.