At one time it was thought that all dogs were colour blind, but modern thinking has changed, but, "they do see color, but their chromatic acuity is significantly less than humans'. This is for two reasons: (1) dogs have far fewer cone cells in their retina (cone cells are responsible for seeing color); and (2) dogs are dichromatic (they see only two primary colors - blue and yellow) whereas humans are trichromatic, meaning we see three primary colors - red, blue, and yellow.
Humans have 7 times higher proportion of cone cells than dogs, meaning that when dogs do see colors, they are pale or