Red smells like a sweaty boy's skin when he is asleep after being exhausted by...

Sex: it smells like sex.

I don't mean to reinforce stereotypes--in fact, I am very partial to the colour.

Sometimes it has an iron smell like blood
Or it smells like the embers of a campfire
Or the thick summer air when it hasn't rained for weeks
Or melted candlewax, soft in the hand...