From left to right: MW, LMC, and SMC stars. Gaia-2MASS diagram coloured by the optical depths τ_V values derived in our study. The dotted lines represent the observational-derived lines delimiting the different regions occupied by different types of AGB stars, and are defined as in Lebzelter et al. (2018). In the left panel, each region has been labelled accordingly with red text. The stars inside the C-rich region are the ones defined in this paper as C-region stars.