Optical/NIR color−color diagram of the 33 quasars from the parent sample, color-coded as a function of their reddening, A_V (see the top legend). The HAQ g−r color cut is shown by the dashed line. This conservative cut yields a reliable sample of reddened quasars only, while more relaxed color criteria are needed to obtain a more complete sample of reddened quasars, see also Fig. 5 (middle and right panel).