Period (in days) vs. BP-RP color for the MS sample with grade 4 and higher; black symbols refer to stars with periods in excess of the estimated break-up period, blue symbols refer to stars with more than 50% of breakup, red symbols to those below. Note: the period scale for periods below 1.5 d is logarithmic. The periods for the stars inside the green dashed lines are not thought to be rotational periods. See text for details.