You get a blue gas flame with a hydrocarbon gas when you have enough oxygen for complete combustion. When you do have sufficient oxygen, the gas flame appears blue because complete combustion creates enough energy to excite and ionize the gas molecules in the flame.

What does it mean when a fire flame is blue?

A blue flame colour means complete combustion. This indicates that the gas is being burned efficiently without any unburned and wasted gas. With complete combustion you get the maximum heat output from your gas and use less gas to generate heat with whatever appliance you are using.

Is blue fire hotter than red fire?

Hotter fires burn with more energy which are different colors than cooler fires. Although red usually means hot or danger, in fires it indicates cooler temperatures. While blue represents cooler colors to most, it is the opposite in fires, meaning they are the hottest flames.