Optical, near- and mid-IR color–color and color–magnitude diagrams of counterparts to X-ray sources in the Collinder 69 cluster and comparison with other samples. Small solid circles – blue and cyan – represent probable and possible (Y?) members of the cluster, whereas solid triangles – red and magenta – correspond to the location of probable (NM) and possible (NM?) non-members. Class II stellar objects are identified as big open, black circles. Previously known members for the cluster appear as green crosses (Class III) or open green circles (Class II), and were selected from Dolan & Mathieu (1999), Barrado y Navascués et al. (2007) and Morales-Calderón (2008). The asterisks represent the location of Taurus known members, with photometry coming from Luhman et al. (2006). The extragalactic samples were selected from Sacchi et al. (2009), and correspond to the SWIRE/XMM-Newton/ELAIS-S1 Field with spectroscopic data. Up- and down-ward open triangles – light gray – correspond to the AGN1 – QSO1, broad lines – and AGN2 – obscured QSO, narrow lines, respectively, whereas open circles – light gray – and three-point stars – dark gray – represent resolved galaxies and Emission Line Galaxies (which include AGN and star-forming galaxies), respectively. The first color–magnitude diagram includes a 5 Myr isochrone – Dusty – from the Lyon group (Baraffe et al. 2002). A reddening vector also has been included.