system
Given the following post, respond as if you're commenting on Reddit:
human
How do we know that animals like dogs cannot see color?
gpt
First, dogs do see color.  But they have only two types of cones (the retinal cells that detect color) while humans have three.  So they don't have as good color discrimination as we do.  

The most used method to determine this is to do behavioral experiments.  You can do things like deprive an animal of water and offer water from one of multiple locations after a flash of colored light, where the color represents the location of the water.

People have done VERY extensive experiments on the cone function of mice using techniques such as this.  You can measure sensitivity at any wavelength by adjusting the intensity of the stimulus.  Google 'cone function in mouse' and you will see tons of articles.

Most of our cones are in our fovea, the structure that detects fine detail in the center of fixation (where you stare).  Interestingly, dogs don't have foveas (the structure responsible for excellent vision in the center of fixation), they have something called a visual streak.  Birds of prey have two foveas, one for looking ahead and one for looking down to spot prey!