NIR (top) and MIR (bottom) colour-magnitude (left) and colour-colour (right) diagrams for M 8. The objects have been colour-coded based on their effective temperature as determined through spectral classification (Sect. 7). The magenta diamonds are the objects with CO bandheads in emission and the black dots the unclassified objects. The specific objects mentioned in the text are labelled with their respective names. The location of the zero-age main sequence at the distance of M 8 is shown with a solid black line (Hanson et al. 1997; Cox 2000). The black-dashed line in the top-left panel represents the reddening line for an O3 V star for R_V = 3.1. Top-right panel: reddening lines of an O3 V (left) and a M0 V (right) star. In both cases the crosses on top of the reddening lines correspond to A_V values of 5, 10, 15, 20, and 30 mag. The grey-dotted lines show the reddening line of an O3 V star for R_V = 5. The dashed line in the bottom-right panel divides the CCD into the areas dominated by YSOs (grey dots) and visible photospheres (orange squares) in the MIRES catalogue (Povich et al. 2013).