Gaia CMDs of NGC 6633 and NGC 6866 proper motion and parallax members. Top panel: blue diamonds mark NGC 6633 members that have been shifted to the absolute and unreddened scale using individual Gaia parallaxes and individual reddening estimates from the 3D reddening map of Green et al. (2019). Small red circles are the members of NGC 6866 shifted in the same way. All giant members of NGC 6633 are marked by a specific blue, green, or yellow symbol with cross reference to Table A.1. The giants members of NGC 6866 are marked with red symbols as in Brogaard et al. (2023). Also shown are MESA isochrones with details in the legend and Sect. 6. Bottom panel: zoom on the upper panel in the area of the giants.