Stars (dots) and isodensity contours (lines) for the two groups spatially segregated by (BP − RP). BG (in blue) contains the objects in segregated bins with colour bluer than 1.5. RG (in red) is the same for colours redder than 4. The RG is mainly associated with the cluster centre, while the BG shows a stellar population with its maximum density well separated from the core of Wd 1. The axes show angular distances in equatorial coordinates.