Tim S wrote:
Andy Champ coughed up some electrons that declared:

Most common sort? Well, colour blindness is an obvious case. But
apparently a few women have 4-colour vision.

Just out of interest, what's the 4th colour?

Some sort of red, or orange, or... how the heck could I describe it?

And for true colour accuracy (though without speed or much resolution)
look at the Mantis Shrimp. IIRC it has sensors for polarisation and a
complete spectrometer build into its eye.

I'm getting that "Geordie" moment

They're eyes Tim, but not as we know them!

Andy