Stars don't actually "burn" gas in the way we think of burning on Earth. They undergo nuclear fusion, which is a different process.

Here's the breakdown:

* Main Sequence Stars: Most stars, including our Sun, are main sequence stars. They primarily fuse hydrogen into helium. This process generates the vast majority of their energy and light.

* Heavier Elements: As stars age and their core temperatures increase, they can fuse heavier elements like carbon, oxygen, and neon. These fusion reactions release even more energy, but they are also much shorter-lived.

* Color: A star's color is determined by its surface temperature, not the specific elements being fused.

* Hotter stars: Blue and white (like Rigel)

* Cooler stars: Red and orange (like Betelgeuse)

Important Note: The fusion of heavier elements doesn't change the overall color of a star significantly. The dominant factor is the star's temperature, which remains relatively consistent during its main sequence life.

So, while stars *do* fuse heavier elements, it's not the primary source of their color. The color is primarily determined by their surface temperature, which is a result of the overall energy being produced by the fusion process.