Distribution of central galaxy colour as a function of cosmic web location and local overdensity. In each panel, a scatter diagram shows the relation between the distance to each critical point of the density field and the local group overdensity (log₁₀(δ)) on 5 h⁻¹ Mpc scales for all central galaxies in our sample, colour-coded by their g − r colour. From top to bottom, the panels illustrate the distribution with respect to the distance to (1) Maxima (d_Max), (2) Filament saddles (d_Fsadd), (3) Wall saddles (d_WSadd), and (4) Minima (d_Min). The contour lines (black lines) represent the progressively lower density levels (down to 5% of the peak value). The horizontal dashed lines (green and magenta) mark the 15th (P₁₅) and 85th (P₈₅) percentiles of the distance distribution, respectively, used to define environment thresholds.