[daedrdev]

Some animals have more cone types than humans, especially various birds, so would probably see a violet sky.

We don't have this because common ancestor for all mammals lost all cones but one, perhaps due to being nocturnal, and a second was re-evolved as mammals became more dominant (after dinosaur extension). A third cone was evolved in primates due to a gene duplication that gave us our green cone

https://www.sciencedirect.com/science/article/pii/S004269890...

[reactordev]

maybe in 100M years we'll get a 4th cone or rod. Probably from nuclear mutation...

[jaggederest]

We already have mutations, generally in women, for tetrachromaticism, who usually have male relatives with severe or moderate color blindness, in which the X chromosome encodes a different green cone. So they end up seeing red, strange-green, green, and blue, where strange-green is somewhere closer to red than green.

Only a few on record but they tend to have absolutely insane color matching and color perception. One of note worked in the fashion industry and could match fabrics perfectly even in varying lighting (e.g. working under fluorescent but able to match colors that would stay matched in halogen/stage lighting)

[int_19h]

There's some evidence that tetrachromacy already exists in a few humans. If so we have the gene already. But why would it spread?

[mr_toad]

> maybe in 100M years we'll get a 4th cone or rod. Probably from nuclear mutation...

There’s a Greg Egan short story (I think it’s ‘Seventh Sight’) where a bunch of formerly blind kids with cybernetic eyes hack the receptors to respond to wavelengths other than the traditional RGB. So perhaps it wont take millions of years.