Blue apples phenomenon

Blue apples is an optical phenomenon in which sunlight on specific days and times shining through stained glass creates colored spots (not necessarily blue). This can be observed in places with large stained glass windows: churches for example.

The term comes from the phenomenon which used to occur in the chapel of Rennes-le-Chateau. It was named after a phrase in a parchment. There is a whole story of mystery behind it and i'm not going into it. If you want to know search for "Rennes-le-Chateau" on Google and you'll easily find it. I'm merely posting because they make nice pictures.