It’s sometimes practically impossible to tell similar colours apart. Even side by side, they look the same. A special pair of spectacles gives us new power to see more distinct colours, and could one day help to spot counterfeit banknotes or counteract camouflage.The glasses, devised by a team at the University of Wisconsin-Madison, basically enhance the user’s colour vision, allowing them to see metamers – colours that look the same but give off different wavelengths of light – as recognisably distinct hues.