This is just a a bit of a field curiosity.  Some days ago my wife spotted a bit of broken branch on the ground that was a curious colour and snapped a picture in the field because it was a vivid green-blue. We eventually found it in a guide book* on the very last page (377). Yesterday she found another bit and brought it home to show me.  

This is the result of a fungus called Green Elfcap (Chlorociboria aeruginascens).  It’s not the fungus itself showing but the mycelium growing through the dead wood stain it this colour.  I’ve not seen it before but apparently it’s classified as common so I guess I haven’t been looking hard enough!

* The book is ‘Mushrooms’ by Roger Phillips. One of the most comprehensive, precisely detailed and beautifully documented photo guides I’ve seen.