Myth: “Gotta go with a gray horse on a gray day.”

We've all had that moment: overcast skies, a gray streak of lightning closing from ten back down the stretch, and everyone in the box yelling the same thing. But is there anything to it — or is it just a great story?

The claim

On a cloudy, rainy, gray day, the gray horse has some kind of edge — it's the romantic pick that keeps a little kismet in the sport of kings.

What we tested

Eight years of races at a top track, dead heats and DQs removed. Coat color came straight from the racing program; weather was split into “Clear” versus “Not-Clear” (rainy, showery, cloudy). Then we looked at both win rate and return on investment by color.

What the data shows

On win rate, there's no statistically significant difference by color — clear day or gray day, grays don't win any more often than chestnuts or bays. Myth busted? Not so fast — the interesting part is the money.

Gray horses post the worst ROI of any coat color, and they're overbet even more heavily when the weather turns. The public believes the legend — so they bet grays down, and the payouts shrink to less than they should be when one does win.

The verdict — BUSTED

A gray horse on a gray day is exactly that — a myth, and one other people believe, which is what makes it expensive. Next time the clouds roll in and your buddies pile on the gray, take the chestnut and let them pay for the privilege of the better story.