system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Some animals are able to see colors we can’t. How do we know what objects would be in a color we can’t see?
gpt
Colour is just the frequency of the light. We know which frequencies make red, green, blue, etc, so we can use light sensors to measure the frequencies coming from other objects and see that they're not in the range our eyes are sensitive to.