And then there is the mantis shrimp with 12 different photoreceptors[0] As for genetically engineering an extra cone, they did that with mice, mainly to addres

And then there is the mantis shrimp with 12 different photoreceptors[0] As for genetically engineering an extra cone, they did that with mice, mainly to address the chicken-and-egg question: if you get an extra cone, does the brain learn to see extra colours? It seems like it would[1]. What you propose would be almost impossible to test though. Sure, you can test for distinction quite easily, but measuring the cost/benefit of it in evolutionary terms is a lot harder. There is a trade-off to make here in what perception the eyes and brain are optimised for, perhaps other forms of perception will suffer to the point of it not being worth it. Also, bad news regarding UV: our cones can perceive it, but our lens filters it out, suggesting it has too many disadvantages. The main reason is likely because UV light creates too much chromatic abberration in a single-lens system, making it hard for us to focus properly[2]. This is not a problem for the kind of vision required by a honey bee, but it would be for humans. [0] http://science.sciencemag.org/content/343/6169/411 http://science.sciencemag.org/content/343/6169/411 [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC208822/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC208822/ [2] https://en.wikipedia.org/wiki/Chromatic_aberration https://en.wikipedia.org/wiki/Chromatic_aberration