How do you know dogs see in color?

Scientists have performed colour vision tests on dogs. Jay Neitz, for example, tested the color vision of dogs. Dogs were shown three light panels in a row: Two of the panels were the same color, while the third was different. The dogs' task was to find the one that was different and to press that panel.

Other research has found that dogs colour-sensitive cones in their eyes, but not as many as a human's. Studies have shown that dogs could not differentiate between green, yellow, orange or red. However, dogs are able to differentiate between various shades of blue and violet.