Left: ﹩V,V-I﹩ color–magnitude diagram of 90Prime sources in W3 with V ≤ 18.5 mag. Sources with Hectospec spectra are denoted by dark gray filled circles, while 90Prime sources that were not targeted for spectrosopic follow-up are shown as light gray filled squares. The solid blue lines are the reddened 2 and 5 Myr pre-main-sequence isochrones from Siess et al. (2000) that were used in target selection. Right: the same color–magnitude diagram with identified O- and B-type stars (see Section 3) highlighted with open diamonds. Overplotted are the reddening tracks (red lines) for B3, B5, B7, and B9 V stars using the extinction law from Section 4.