Comparison of some of the observed colours for all the regions in the sample (coloured points) with the colour space covered by the models (grey hexagons). The selected colours are representative of young and old stellar populations and of the dust. The colour of each dot indicates the galaxy following the colour bar on the right. The density of models is indicated by the shade of the hexagonal bins, following a logarithmic scale. Black indicates the highest density of models, whereas white indicates the absence of models in the particular bin.