While the question is overbroad considering the millions of animal species including insects, the general answer is that scientists have reason to believe many if not most animals see in color to some extent. For simplicity, a very general rule is sometimes offered: most diurnal animals do see in color, while most nocturna animals don’t, but even here there are exceptions.
Animals and insects cover an exhaustive field of biological diversity. The majority of spiders have eight eyes and poor vision, while flies have hundreds of tiny lenses and near-360-degree vision. Eagles can spot a mouse from over one mile high (1.6 km), while a sloth has trouble seeing any animal that isn’t moving. Considering this vast diversity, whether or not animals see in color is a question that must be taken species by species.
In humans, rods and cones in the eye’s retina detect light and color, respectively. Rods allow us to see shapes in dim light and make our way down the hall in the middle of the night. Cones, which detect color, require more light to activate. For this reason you might notice that you don’t see color in the dark; instead, everything appears in shades of gray. Flip on a light, and the retina’s cones activate, relaying color information to the brain.
When considering whether animals see in color, one approach is to look to the structure of the eyes to see if cones are present. Many nocturnal animals that scientists have studied lack cones, relying instead on greater numbers of rods for extended night vision and keener detection of movement. As an exception to the nocturnal rule, owls do have cones, leading scientists to believe these animals do see colors. Most species of primates, birds, cats and dogs also see in color to some degree.
Humans have three sets of cones for detecting color in different wavelengths: cones that detect red wavelengths, cones that detect blue, and cones that detect green, though each cone detects a wide spectrum that overlaps to create other hues. Animals like cats and dogs have two sets of cones, making them color-blind to specific colors. They do, however, have many more rods than humans, giving them greater night vision and a keener ability to detect motion.
For example, dogs can’t distinguish between green and orange which will both look grayish. Toss a bright orange tennis ball across a green lawn and you’ll find a dog can follow it fine while it’s in motion. Once it comes to rest a distracted dog might lose the ball against the background. Only its shape will cause it to stand out. In humans, green color blindness is referred to as deuteranopia.
Feline animals see in color, but they have trouble distinguishing reds; the human counterpart being protanopia. Reds appear as differing shades of gray to a cat. It is believed both dogs and cats see mainly in grays, yellows, and blues.
Honeybees and butterflies have three pigment visual receptors with true color vision within their visual spectrum. This spectrum stops short of the infrared but extends into the ultra-violet beyond human vision. Not only can these animals see colors, they can detect a mix of colors as well as pure colors.
It is believed coral reef fishes see close to the same rich spectrum of colors that humans see, as evidenced by the many colors present in a coral reef environment. Though not an iron clad assumption, the animal kingdom has evolved bright coloring to both ward off predators and attract mates – an evolutionary feature that would seem to be lost on animals that cannot see color. However, exceptions exist here too and the assumption is somewhat general and speculative.
Sea mammals like sea lions, dolphins and whales possess a single type of cone for detecting patterns in light, but not colors. This is known as cone monochromacy and these animals are believed to be totally color-blind.
While it might be true that the animals we most closely associate with do not share the same rich spectrum of colors that humans enjoy, it’s probably safe to say that many diurnal animals see in color to some degree. Hence, the next time you find yourself walking down the aisle of your favorite pet store with your cat or dog in mind, you might pass up the red, green and orange toys to get something in a nice, bright shade of blue or yellow.