(B − V, V) color−magnitude diagram for HD 163296. Datapoints span the period 1983−2012; see Fig. 5 for the coverage of this epoch. Only points with errors <0.1 mag are plotted. Fading events in 1988, 1991, 1993, and 2000 (letters correspond to Fig. 5) are highlighted with colored symbols. During these events, the colors change along the extinction vector (Cardelli et al. 1989), which is plotted for R_V = 3.1 and R_V = 5.0. The origin of this vector, indicated with a red cross, represents the intrinsic colors and magnitude of an A1V star at 119 pc (Kenyon & Hartmann 1995).