Colour–magnitude diagram of group dwarfs (top; orange for T21 and green for T24) and field dwarfs (bottom; orange for T21 and green for T24). Background galaxies removed using colour selection (red) and using the surface brightness–magnitude diagram (pink; see Section 3.2.2) are included. The grey shaded region is the region removed by the g − r colour selection. Fornax cluster dwarf galaxies from Su et al. (2021) are plotted to highlight the red-sequence (black).