Hertzsprung–Russell diagram
In general, the temperature of a star relates to its color. At the top of the chart, along with the temperatures, are the spectral classes. The hottest stars are blue-white (class O), those in the middle temperatures are yellow (class G) and the coolest ones are red (class M). When we say "coolest" about stars, the lowest temperature for a star is almost 5000 degrees Fahrenheit.