Optical and near-infrared color–magnitude diagrams for M 25 and NGC 7790. For M 25 the blue and black filled circles are X-ray and bright U-band selected sources, respectively. Color cuts were made to reduce field star contamination. For NGC 7790 the black filled circles are 2MASS (near-infrared) and ARO (optical) field decontaminated photometry (Bonatto & Bica 2011, and references therein). Black dots in the color–magnitude diagrams represent the intrinsic relation (Majaess et al. 2011b) shifted to match the observations. Optical photometry for the cluster Cepheids are conveyed by circled dots (Berdnikov et al. 2000; Berdnikov 2008).