system
Given the following post, respond as if you're commenting on Reddit:
human
Why is blue the last color to fade in sunlight?

I often see posters in shop windows that have been faded by the sunlight that hits them every day. Blue always seems to be the last color to fade  out, so you're left with this strange blue/white picture.

Why is this? Is it something about a common blue dye that is used in printing? Is sunlight weaker in that part of the spectrum?
gpt
Because the blue coloring agents *reflect* the higher-energy light from the blue end of the spectrum rather than absorb it, and so they avoid being broken down into colorless molecules longer than the others.