Color-color diagram (H – K, J – H) for 561 variable stars. The NIR colors are from the 2MASS Point Source Catalog. Green dots: 162 objects matched to Mo-Call, Blue dots: 106 objects matched to Fnl3, Red dots: 62 objects matched to Fnl7, Yellow dots: 267 objects matched to K23, Megeath et al. (2012), Großschedl et al. (2019), and others (see text). Black dots: 105 objects without any youth indicator in the literature. Bona fide TTS are marked by crosses; CTTS (red), WTTS (blue). The solid curve represents the locus of main-sequence stars from Kenyon & Hartmann (1995); the red dashed lines are reddening vectors for A_V = 10 mag. The black dash-dotted line is the locus of unreddened CTTS from Meyer et al. (1997).