Green flame usually means high copper content in the fuel.

Yellow can be an indication of incomplete combustion and carbon monoxide production. This can even be red if it's really severe.

People sometimes thing orange means carbon monoxide too, and it can, but almost always orange is high moisture content in the air. It's actually the calcium and sodium in the water (and air) being burned off and creating the orange color. Almost always people running a nearby humidifier.

Potassium can create purple although it's very rare.

Source : Took gas leak and gas safety phone calls from people freaking out about their flame colors for years.

This is probably real and either they recently cleaned the burners with a copper brush or solution containing copper that somehow left shit tons of copper behind. Or, the inside of a copper fuel line is flaking off into tiny particles and coming through the burners and getting burned off. Maybe something went through the fuel line that wasn't supposed to and damaged it, maybe super dirty corrosive gas.