  We determine the phase diagram of mixtures of spherical colloids and neutral
nonadsorbing polymers in the thermal crossover region between the $\theta$
point and the good-solvent regime. We use the generalized free-volume theory
(GFVT), which turns out to be quite accurate as long as $q = R_g/R_c\lesssim 1$
($R_g$ is the radius of gyration of the polymer and $R_c$ is the colloid
radius). Close to the $\theta$ point the phase diagram is not very sensitive to
solvent quality, while, close to the good-solvent region, changes of the
solvent quality modify significantly the position of the critical point and of
the binodals. We also analyze the phase behavior of aqueous solutions of
charged colloids and polymers, using the extension of GFVT proposed by Fortini
et al., J. Chem. Phys. 128, 024904 (2008).
