Do pets really prefer brightly coloured toys? Pets see limited colours compared to humans. Dogs are thought to distinguish blue from yellow, but do not differentiate between red, orange and green. Cats can see blue and green, but not red. Pets’ eyesight excels in dim light and in sensing tiny movements. Cats’ large eyes require only one-sixth of the light that humans need to see. Dogs and cats also have a reflective lining at the back of the eye.