Contour plot of XGBoost predictions (z̃) versus catalogue redshifts (z) coloured by density in the (z,z̃) space for HIEROs (left panel), red HIEROs (middle panel), and blue HIEROs (right panel), all of which have H_E ≤ 26. Lighter contour colours indicate higher densities. The dashed red lines show z̃ = z ± 0.15(1 + z). The percentage of objects with respect to N_test is indicated in the bottom-right corner of each panel.