Flickr user jbum has an image of saturated and unsaturated samples of photos with varying tags. OK, in English he looked at pictures that were tagged different things. And then found the average color.
From his notes on the tag color graph photo:
"For each keyword in this picture, I downloaded all the matching thumbnails, up to a maximum of 1000 images, and averaged the colors, using a script.
The left side of each stripe is the resulting color.
The right side of each stripe is the same color, with the saturation cranked up.
Now, I must admit, when I began this experiment, I was really hoping for a more obvious result: money = green, spring = green, sex = pink, winter = white, death = black. Something like that… Right?
No such luck. Reality, as always, rudely intrudes."
From the comments, also worth looking at is The Color of Palo Alto art project.