Star color is a function of surface temperature 🌟 🔴 The color indicates how hot the visible "surface" of the star is. The coolest stars are red, with surface temperatures of about 3,000ºC. 🔵 As a star's temperature rises, because there is more gas in the star — and therefore more fuel to burn — it becomes hotter. Its color changes from orange to yellow to white. The hottest stars are blue, with temperatures up to 40,000ºC. Explore the stars and other celestial objects with the Sky Tonight app