Top: high (solid shapes) and low ionisation (open shapes) sources from the inner (red triangles) and outer (blue squares) regions are plotted on a CMD of the AGB sources from Paper I. The horizontal and vertical lines mark the selection criteria used in that paper. The green pentagon marks the position of NGC 6822 SySt 1 (Kniazev et al. 2009). Bottom: same sources plotted on a (H − K, J − H)₀ colour–colour diagram. The horizontal and diagonal lines mark the selection criteria used in Paper I.