The colour of the stars reflect the age of the stars.
Now red indicated that the stars is aged. color is reflected from the fusion reaction it indicated the temperature. if the temperature is high then the star is young. the star will be blue during young stage which indicates high temperature and the nuclear fusion reaction is going on very fast. if it is aged the color intesity will decline till red which shows low temperature due to less fusion reaction.
The color of a star is an indication of its brightness, temperature, and age. Stars are classified into groups called "spectral types." From oldest to youngest and hottest to coolest, the types of stars are:
Each spectral type is further subdivided on a scale of 0 to 9. The sun, for instance, is a type G2 star.
Sources: The Guinness Book of Answers, 8th ed., p. 11; Rovin, Jeff. Laws of Order, p. 214.