When sulfur is heated in oxygen, it burns with a bright blue flame and produces sulfur dioxide gas.

Here's why:

* Chemical Reaction: The reaction between sulfur and oxygen is a combustion reaction. This means that sulfur reacts rapidly with oxygen, releasing energy in the form of heat and light.

* Blue Flame: The blue color of the flame comes from the excited sulfur atoms emitting light as they return to their ground state.

* Sulfur Dioxide: The product of this reaction is sulfur dioxide (SO₂), a colorless gas with a pungent odor.

So, while the heated sulfur itself is not changing color, the flame produced during the reaction is a bright blue.