The color of a flame depends on several factors, including the temperature and the substances undergoing combustion. The hottest part of a flame is typically the base, and blue flames are the hottest, followed by white flames. When all flame colors combine, the color is white-blue, which is the hottest. The color of a flame changes as the temperature increases, with the colder part of a flame being red and transitioning to orange, yellow, and white as the temperature increases. The transitions are often apparent in fires, in which the color emitted closest to the fuel is white, with an orange section above it, and reddish flames the highest of all. While red flames may reach temperatures up to 1,112 degrees Fahrenheit or higher, blue flames can burn at temperatures up to 1,984 Fahrenheit. The hottest fire color seen by the human eye is violet, as this is the highest energy visible flame color on the spectrum.

In summary, the hottest flame color is blue, followed by white and violet.