found a fallen tree in the woods today that was blue on the…

It's a fungus! 🍄 a type that decomposes dead wood.
Perhaps a kind of Chlorociboria :)
The wood is blue due to the pigment produced by the mycelium 💙

Aha wow look at that, very interesting and cool at the same time! Thank you so very much for that knowledge! So fascinating with fungus 🍄🙏