Photometric redshift results as a function of the r − i and g − r colours. These results were obtained with a 100-fold cross-validation strategy on the set of galaxies with the five magnitudes available (𝒯₅). Left panel: average standard deviation of the redshifts of the nearest neighbours σ(z_NN), middle panel: rms of the actual error z_phot − z_spec, and right panel: average estimated errors δ_zphot. For easier comparison, the scale in the three panels was set between 0 and 0.1, with red indicating errors that are bigger than or equal to 0.1. For reference, the black lines represent the contours of the galaxy count distribution of the training set 𝒯₅, with the four displayed contours corresponding to 1000, 300, 100, and 10 galaxies per colour bin.