system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What causes white/grey products to turn yellow over time?

I have an iPhone 6 silicone case that was white but is now leaning towards a very faint yellow color (or at least less white than it used to be). Similarly, my friend busted out his SNES the other day and instead of the grey I've seen on other models, the plastics on his were pretty much yellowing. What gives? How can you prevent this from happening?
gpt
Plastics include chemicals that are there to make the plastic harder to burn. These chemicals include the element Bromine. Sunlight, specifically ultra-violet light, breaks down these chemicals and exposes the bromine, which has a yellow color.