Colour–colour diagram for Masgomas-6. Black dots show the position of the most probable cluster members, and grey symbols show the position of the field stars. Objects with spectroscopic data are shown: massive stars (in green) and late-type giants (in red). In the figure we included the projection, following the extinction law by Rieke et al. (1989) (with R = 3.09; Rieke & Lebofsky 1985), for an O giant (blue solid line; intrinsic colour by Martins & Plez 2006) and a G5 giant (red dashedline; intrinsic colour by Cox 2000). The stellar population located above the red-dashed line corresponds mostly to the disc giant population and is observed only in the grey-field stars. The massive star population, confirmed spectroscopically, is observed close to the blue solid line and below the giant sequence.