Here in the U.S., our eggs mostly come in two colors: white and brown. But there are two breeds, one in Chile and one in China, that are known to lay blue eggs. Yeah, weird, right? And a new study has figured out why that happens.

The Araucana chicken from Chile and the Dongxiang and Lushi chickens from China (none of which are particularly common in North America) are known to lay pale-blue eggs. This is rare for a chicken; while bird eggs can come in all sorts of colors and patterns, chicken eggs are almost always white or brown. So what's the deal?