P_rot vs G_BP - G_RP diagram. The S_ph value is colour-coded for the stars for which Gaia and K2 rotation measurements are cross-validated. The stars for which the measurements are consistent are shown in orange. In the left panel the sample is compared with the density distribution of the Kepler stars from Santos et al. (2019, 2021) (in grey), while in the right panel it is compared with the density distribution of the stars from Gaia DR3 (in grey).