Originally Posted by HarryT
I don't believe this is true, but if you do find a reference I'd be interested to read it.
I'm curious myself. It's entirely possible that I have misremembered the whole thing and it is something hypothetical, such as the tetrachromacy as mentioned by meeera above. It's also possible that it was something I read in a newspaper however I am generally skeptical when reading science news in newspapers (even reputable ones) as the articles are usually so truncated and superficial that they are close to being untrue.