[[Fire]] that is predominately of a [[blue]] color. Although real-world fire can turn blue "if it's burning hot enough":[https://en.wikipedia.org/wiki/Fire#Temperatures_of_flames_by_appearance], or if there are "certain chemicals in the burning material":[https://en.wikipedia.org/wiki/Colored_fire], occurrences of blue fire in media are usually a visual shorthand to indicate that the fire has some kind of supernatural quality to it.
青い炎