r − z color as a function of the quasar redshift (left) and the r − z color distribution (right) for DR9 quasars without BALs or a DLA along the line-of-sight (black), associated DLAs without an emission detection (red), and associated DLAs with narrow Lyα emission detected (cyan). In the color plot, the median and 1-σ colors for the DR9 quasar sample are shown as magenta curves.