system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why was purple pigment history difficult to produce? Couldn't ascestors have just mixed red and blue, instead of laboriously extracting it from sea snails?
gpt
The blues they had access to were mostly bluish-greens. The reds they had access to were mostly reddish-oranges. When you mix those, you get sort of a baby-poop brown color instead of purple.   


The \*REALLY\* deep reds, deep blues, and deep purples almost all came from the same snails, just fermented differently. (There's one deep blue that came from the indigo plant, but it was almost as valuable as the snails).