BP/RP excess filter applied to the members. Left panel: the C−(G_BP − G_RP) relation. The majority of stars in Sco OB2 are below the fitted curve, thus the filter C < 1.22 + 0.04(G_BP − G_RP)² selects the stars with good color quality, painted in blue. The stars excluded by the filter are colored in gray. Right panel: the color-magnitude diagram after filtering. The stars that passed the filter are plotted in blue, those excluded in gray. The black dashed line indicates the zero age main sequence (ZAMS) from the PARSEC model.