Google is testing new red colored review stars in their search results, a change from the usual yellow-orange stars we normally see.  It is a dark red shade they are testing this time.

Dan Barker posted this screenshot to Twitter.

It doesn’t show if this test is restricted to just Google AdWords ratings or all AdWords and organic results, however during testing in the past, Google has changed tested the same color for both AdWords and organic.  Google has periodically used and tested various colors of stars, including different shades of yellow/orange as well as green.

Bing has also done extensive testing of star colors in their own search results too.

It is very likely this is just a small percentage based test to see how different colored stars are performing right now.  I was not able to reproduce them.

Added: They are appearing in the organic search results too.