Components of the OC system at the colour-magnitude diagram. Probable members of Cr 135 are shown with red dots, probable members of UBC 7 are indicated with blue dots (left panel), and probable members of the extended halo are shown with yellow dots (right panel). Grey dots are for background stars. The green line represents the isochrone for 50 Myr for single stars, and the magenta line is for the same isochrone for unresolved binary stars with identical components. The red line is for the zero-age main sequence.