CMD of member stars of Bo 7. The MS stars among O6.5 and B0 are identified with light blue triangles, the MS stars among B1 and B6 are identified with yellow triangles, and the luminosity class-III stars among B0 and B2 are identified with yellow open triangles. The thicker continuous curve is the Schmidt-Kaler (1982) HR diagram for early stars; the other curves are Marigo & Girardi (2008) isochrones for z = 0.02. All the reference curves are corrected by an apparent distance modulus of 13.7.