Funny dog comic.

Are dogs color blind? Well not exactly, “No, dogs are not colorblind in the sense that they see more than just black, white, and gray. However, the color range they perceive is limited compared to the spectrum we see. To put it in very basic terms, the canine color field consists mostly of yellows, blues, and violets. “Human” reds, greens, and oranges are not distinguishable to dogs and instead appear somewhere on their yellow to blue spectrum.”

From dogtime.com.