New Scientist teaches you how to make yourself synaesthetic:
Olympia Colizoli at the University of Amsterdam in the Netherlands, and colleagues… gave seven volunteers a novel to read in which certain letters were always written in red, green, blue or orange…. Before and after reading the book, the volunteers took a “synaesthetic crowding” test, in which they identified the middle letter of a grid of black letters which were quickly flashed onto a screen.
Those with synaesthetic training aced the test. Those stuck with a black-and-white worldview didn’t.