Colour–magnitude (left) and free-reddening parameter–magnitude Q_IR (right) diagrams for Masgomas-6. Black dots show the position of the most probable cluster members, and grey symbols show the position of the field stars. We include in the figure the spectroscopically confirmed massive stars with green open squares and the late-type giant stars with red open circles. The individual identification numbers (ID, Table A.1) are also shown above each coloured symbol. In the pseudocolour–magnitude diagram, we can see that most of the massive stars are found between Q_IR values of –0.2 and 0.2, as expected from our selection method.