Observed NIRCam colour–colour distribution of galaxies at 5.8 < z_phot < 6.2 in the CEERS and NGDEEP fields (grey points and open circles), compared with the SPHINX²⁰ DR z = 6 galaxies used in our analysis (red points). The SPHINX²⁰ galaxies trace the same region in the F150W-F277W versus F277W-F444W plane as the observed population, indicating that their broad-band colours are consistent with those of typical star-forming galaxies at z ≈ 6.