Green flame usually indicates COPPER, so it could have been a piece of space junk with electrical contact materials.....................
Actually not in this case.
In meteors, it indicates speed. Blue is the fastest, red the slowest.
Meteors don’t oxidize, like wood in a fire. They just heat up to a melting point and vaporize. The faster they are coming in, the closer to blue they get.
I saw an Orange one a few years ago. We were at our dark sky site and it started off as a nice meteor, then, it flared out and turned Orange! It was seen all over South Georgia and North Florida.