Colour–magnitude diagrams for all galaxies within 300 kpc and 1 Mpc. Galaxies with spectra are shown as triangles (this work) and squares (literature). Small dots are photometrically classified SDSS galaxies with i′ < 21 mag. Filled symbols show spectroscopically confirmed group members whilst open ones are background galaxies. Group members form a tight red sequence of  ~0.4 mag thickness. The dashed lines show the adopted upper limit of this sequence g′ − i′ =  −0.05317 × i′ + 2.36. Vertical lines show the magnitude limit (i′ = 20 mag) for the spectroscopic target selection.