Just saw one yesterday while coming in to land at Strathallen (EGAU if I remember correctly) - as I’m losing altitude the ground starts popping in significantly lighter tiles, but then as I get even lower they start to change back to the original colour.
So I had the effect of tiles a few tiles in front turning light then being redrawn darker again as I got closer 
It seems like it’s a dynamic weather effect that isn’t quite working correctly after also seeing the snowy tiles popping in around Courchevel a while back…