Colour-magnitude diagrams (J-Ks) vs. Ks for the extended objects in tile b204 (red dots) and G21 galaxies (blue dots). We consider VVV extinction-corrected aperture magnitudes. Crosses show galaxies not detected with our methodology, with the sources lost by the (J-Ks) cut in pink, sources with R_1/2 < 1 arcsec in cyan, and galaxies with unreliable measurements in the Z and Y VVV bands in yellow. On the right-hand side of this figure, we plot a densogram based on the (J-Ks) colour distribution of the sources. In the upper panel, we show the fraction of recovered G21 galaxies as a function of Ks magnitude. Error bars are associated to standard errors.