Observed (g – r) vs. (u – g) colour-colour diagram for the 1 deg² mock sample (first row) and miniJPAS observations (second and third rows). Stars, galaxies, and QSOs are predicted classes with the ANN₁ in miniJPAS observations, while they are true classes in the 1deg² mock sample. The dots in the third row are colour-coded according to the SExtractor probability developed to separate between point-like sources (CL > 0.5) and extended sources (CL < 0.5). Each column includes objects at different magnitude bins.