M. Murphy, and M. Bernet. (2015)cite arxiv:1510.05667Comment: Accepted to MNRAS. 18 pages, 17 figures, 5 tables. Tables 1-4 available in the published electronic version or from http://astronomy.swin.edu.au/~mmurphy/publications . Code emulating the SDSS colour-selection algorithm is available at doi:10.5281/zenodo.31470 (http://dx.doi.org/10.5281/zenodo.31470) and hosted on GitHub (https://github.com/mbernet79/SDSS_QSOsel_Bernet).