Microwave phenomenon

Droes

Hello, I saw this experiment on Youtube , and I was wondering what reaction is going on here.

I also saw a variant of this (can't find the video though), in which the plasma existed for 57 seconds, when it changed colour to blue with some white sparks in it, a few seconds before dissolving. Does anyone know why it changed colour?

Thanks in advance!
If I I posted this in the wrong subforum, could an admin move it please?