Why are Irish Setters so red? Geneticists at the UC Davis School of Veterinary Medicine now have an answer for why some dogs have more intense coat colors than others.
While their wolf ancestors are muted in color, domestic dogs have been bred into a variety of hues from white and golden through brown to black. Similarly to other mammals, canine coat color comes from two pigments: yellow (pheomelanin) and black (eumelanin). These pigments are controlled through pigment-switching genes MC1R (melanocortin 1 receptor) and agouti signaling protein (ASIP). For example, solid yellow or red dogs have a mutation in MC1R so they only make pheomelanin.
via Whisker Therapy