Here's a history of modern art in color use, courtesy of Martin Bellander, a PhD student in psychology at the Karolinska Institutet. Culled images from this BBC directory, Bellander has charted colors in 94,526 paintings from 1800-2000. As you can see, art has progressed to blue:

Art is getting bluer . Image 1.

Bellander speculates about a few possible causes of increased blue use: blue is expensive; an increade of blacks which register as blue in cameras; resins age and yellow over time. (For a code-heavy technical run-through of his research process, check out his process here.)

We'd add to that, the increased availability of new blue pigments, a lessened focus on portraiture (with lots of pink skintones), and more use of pure, unmixed pigments in modern art. Or maybe just zeitgeist.

Probably unsurprisingly, red remains steady. The best-selling paintings are red