Blue main sequence stars had a greater initial mass.
Explanation:
Color as indicator of temperature. Blue represents a hot a star that is a star with very high temperature. On the other hand, a red color star represents a cool star. The initial mass of a blue main sequence must be greater than the initial mass of a red main sequence star. For high temperature, more fuel must be burnt which means greater initial mass. A blue main sequence star is a hot star and must have greater initial mass, so it burns more fuel and has high temperature as compared to the red main sequence star.
