Intellectual property law allows for what's called "trade dress" - the visual distinctiveness that, the hope is, allows consumers to differentiate between similar products on the basis of their origin. That means you can walk into the supermarket and spot a red Coca-Cola based on its redness - and know you're not going to open the can and have a swarm of killer bees fly into your mouth. Or, y'know, some weird inferior brand of soft drink. So a rival soft-drink maker can't make bottles of the same hue, hoping to piggyback on Coke's visual reputation.
Coke owns, to a certain extent, that colour. It's a wacky idea - having even partial ownership over the way light reflects off a surface and hits our eyes - but don't worry, nobody actually owns the colour. In the case above, 3M could only stop you from selling a competing product dressed up in the same purple packaging. Other than that, purple is yours to love and own. Go ahead, buy those purple pants - no legal goons will come knocking. [via Boing Boing]