Color−magnitude (top) and color−color (bottom) diagrams of NGC 3766, limited to magnitude and color ranges of interest to the periodic stars studied in this Letter. Indicator symbols, colors and labels have the same meanings as in Fig. 2. Stars for which no spectra is available in this program are plotted in black for periodic variables and in gray for non-periodic stars. Stars labeled in Fig. 2 are reported in the diagrams, as well as the highly reddened non-cluster member star 295.