Dogs and cats can see color, but their eyes lack the cone cells necessary to see red and green. This condition is also the most common form of color blindness afflicting humans (protanopia).
I happened upon a website that allows you to select an image from your computer and covert it into what a human with protanopia (or other forms of color blindness) would see.
The image on the left is what a human with normal eyesight would see and the image on the right is what a dog or cat would see. Cats have a lower density of color receptors so the colors they see are less vivid.
You can use the colorblind simulator set to protanopia to convert images of your dog’s and cat’s toys lying on the floor to see how they appear to them.
Recent experiments show that dogs do respond to particular colors. Perhaps cats do as well, who knows.
A toy that has more contrast relative to the floor (or lawn) is easier for your pet to find and chase. Red toys only work against light colored backgrounds while a blue toy is the best color to use when playing fetch out in the grass. Yellow toys would spark the most interest against blue or red backgrounds.
A red toy on a burgundy carpet or an orange toy on a green carpet would be virtually invisible to your pet.