VLT/ISAAC NIR colour–magnitude and colour–colour diagrams of N 66, with the positions of the selected sources for spectroscopy marked. For sources C and E, the Ks magnitudes are from LCO observations. The three sources correspond to the brightest infrared excess sources in their respective molecular clouds. The green and red solid lines in the colour–colour diagram are the dwarf and giant locus respectively.The reddening track of a normal O3 V star and Cool Giant G is plotted as dashed black lines. The ZAMS between B5 and O3 at the distance of the SMC is indicated with a solid black line.