What does red mean?

What does the colour red "mean"?

We've just past St. Valentine's Day, and the unavoidable connection to love. Red is also associated with other emotions including anger and rage.

In branding the colour is associated with Coke, Ferrrari, and HSBC, among hundreds of others.

But since when has it been associated with down? I saw this light on the elevator at the library and wondered why the down arrow was red. (By the way, the up arrow was green.)

There are hundreds of associations with the colour red. Stop signs, a whole host of brands, warning etc., and now the down elevator. I wonder how much this confuses people? And if it does confuse people, why is red still such an appealing colour for brand identity?