Colour-magnitude diagram of the SDSS NYU-VAGC (Blanton et al. 2005a). The black lines show contours of the same density of galaxies in this space. The red, green, and blue solid lines show the mean of the distributions of the three Gaussian fits to the (g01 − r01) colour distributions as a function of absolute magnitude. The dotted lines show the position of the mean ± the standard deviation of the Gaussian distributions.