system
Given the following post, respond as if you're commenting on Reddit:
human
If grass turns brown when it dies, why do grass stains stay green?
gpt
Plant leaves are basically made up two types of photosynthetic pigments: chlorophylls and carotenoids. Chlorophylls gives green color while corotenoids gives brown. In young leaves, the no. of chlorophylls is dominant, so it is green. As the plant gets old, chlorophylls degenarate and carotenoids become dominant. So it gets brown.
However a grass stain is literally dead, so the chlorophylls dont degenate, and remain as it is.