It happened 7 years ago, so when it happened recently Photographers were grabbing their cameras and shooting away.

Blue Ice near the Mackinac Bridge.  It is blue, and something you don't see everyday.  Well, it is a bit more common by the National Lakeshore in Lake Superior, where blue ice turns up near the Ice caves.

The ice only appears blue when it is sufficiently consolidated so much that air bubles do not interfere with the passage of light.  I could get more nerdy, but lets just say it is beautiful and something you should see, in person.