Top: variability amplitude V_P90 against the intrinsic colour (G_BP − G_RP)₀. The colour coding is according to the exposure and filter combination (blue: V 120 s, green: I_c 60 s, orange: I_c 600 s, same as in Fig. 2). Stars with derived periods are highlighted and additional cluster members are shown in the background. Possible binaries (radial velocity and photometric) are indicated with additional small black dots. Bottom: fraction of periodic stars as a function of colour for the different exposure and filter settings. The black line marks the overall detection rate. (It is lower for certain bins because of the additional members introduced by the deep outer fields).