O ring color is usually indicative of its material.
I prefer silicone o rings for glow fuel.
BLACK usually indicates Buna O-rings, also known as nitrile or NBR O-rings, offer excellent sealing and mechanical properties at a low cost. Buna O-rings have resistance to common lubricants and are recommended for crude oil, gasoline, propane, petroleum oils and water.
ORANGE is usually silicone