(U − V) rest-frame color distribution for red galaxies as a function of increasing overdensities (horizontal panels) and increasing mass (vertical panels). The mass was divided into three ranges, log ₁₀(M/M_⊙) < 10.25, 10.25 ≤ log ₁₀(M/M_⊙) < 10.6, and log ₁₀(M/M_⊙) ≥ 10.6 (panels from top to bottom), while the quartiles of environment are shown in Tables 1 and 2 (panels from left to right). In each panel, the solid line represents the median of the distribution, while the dashed line is the median value corresponding to the color distribution in the same mass range but for the lowest environment, to make it easier to follow the environment dependence. In each panel, we also report the value of the median (U − V)_rest with its error.