Photometric redshift division with SOM. Left: the two-dimensional projection of the galaxy colour groups constructed with the SOM. The colour scale indicates the mean redshift of the SOM cells, which we define as colour groups. The red spots identify the cells with σ_z < 0.20. Right: the colour groups sorted by their mean redshift. The error bar represents the standard deviation of redshift, σ_z, in each group. The groups with red error bars are the one with σ_z < 0.20.