Distribution of the r − i versus i − z colours of sources around W2246–0526 at z = 4.601. The red filled circle, grey and blue dots, and the magenta line have the same meaning as in Fig. 7. Brown filled squares and cyan filled stars are the confirmed and potential companions detected with ALMA observations (Díaz-Santos et al. 2018). The description of the selection function is the same as in Figure 6.