Slopes of the colour − density relation linear fits for the 23 Cmocks and the 23 Omocks for galaxies with M_B ≤  −20 in the four redshift bins (label on the top), as in the third row of Figs. 7 and 8. Red and blue small diamonds: red and blue galaxies in each Omock; light purple and cyan small diamonds: red and blue galaxies in each Cmock. Red and blue big triangles: mean values of red and blue small diamonds, with the vertical error bar being the rms among all 23 mock samples. Light purple and cyan big squares: mean values of light purple and cyan small diamonds, with their rms. Orange and green circles: slope and its error for VVDS observed data (from C06) for red and blue galaxies, respectively.