Scientists teach mice to see in color

From Nature:

Simply by inserting a piece of DNA that codes for a human eye pigment into the genome of a mouse,scientists have introduced a rainbow array of colour to the dull mix of yellows, blues and greys that normally make up a mouse's visual world.

This suggests that the mammalian brain is very flexible and can interpret signals not normally encountered. It also hints that just a single genetic mutation could have added reds and greens to the visual palette of our ancestors tens of millions of years ago.