system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why are blue light signs so grating to the eyes in comparison to red light signs? When I'm on the road red signs feel more easy on the eyes for some reason?
gpt
It’s a complicated topic, but one of the reasons is because blue light has more energy than other colors. While purple has even more energy than blue, a lot of purple is invisible because of UV. Older blue lights weren’t as bright because they were incandescent lights with a blue filter, rather than true blue light.