Stars of which color have the highest surface temperature?

Stars of blue color have the highest surface temperature.

Scientists have been able to approximately determine the temperature of stars based on the spectrum of a black body, which absorbs all radiation. So, based on that system, they figured out that the stars with the lowest temperature are red stars, their temperature being about 3,000°C, while the hottest stars are blue with the temperature of 7,000 + °C. For reference, the Sun is a yellow star with the temperature of about 5,500°C.