I don't know about you, but I definitely give consideration to what color toy, harness, and bed I choose for my pet. Now, it's not because I truly believe he prefers a turquoise harness, indigo ball, or lime-green pinstripes on his chocolate-brown bed, I would just rather the stuff match my apartment (neurotic, I know). I can't tell what colors North's eyes see, but there's much research (and many misconceptions) about which colors, if any, are visible to doggies. Veterinary ophthalmologists have determined that dogs are similar to people with red/green color blindness — pups can see bluish and greenish shades but not many ones closer to red.
To learn about conclusions from experiments performed by University of Wisconsin researchers, read more.
The retinas of people who see colors normally have three types of color receptors, or cones, and each are particularly sensitive to a narrow part of the spectrum. However, doggies (and red/green colorblind humans) have only two types of cones, giving less basis for comparison and a more-limited perceived color range. People who see colors normally see the traditional VIBGYOR (violet, indigo, blue, green, yellow, orange, and red) spectrum like on the above kite. Dogs, however, see VIBYYYR (violet, indigo, blue, yellow, yellow, yellow, and red). This means that the colors of green, yellow, and orange look alike to dogs but different from red (which they can distinguish) and variations of blues and purples. Pups are actually best at telling shades of violet, indigo (he loves that ball!), and blue apart. However, the results also say that blue-green looks like white to dogs. Oops, guess he doesn't find his harness half as fashionable as I do!