f_blue for stacked clusters as a function of cluster-centric distance (r/r₂₀₀) for different bins of redshift (increasing rightward) and galaxy mass (increasing downward). The computed value of f_blue already takes into account the mean aging of stars with increasing redshift by defining the color compared to an exponentially declining SFH model with τ = 3.7 Gyr. Error bars represent the shortest interval including 68% of the possible posterior values for f_blue. Radial cluster-centric bins are indicated by gray filled triangles on the x-axis and horizontal gray dashed lines indicate the minimum and maximum allowed values for f_blue. Yellow shaded areas with a solid blue line represent the posterior mean and 68% confidence interval of the modeling of Eq. (3), fitting the 225 individual f_blue measurements. Yellow slanting hatched areas with a dashed blue line represent the prediction/extrapolation of this model for bins where we do not have data. Cyan vertically hatched areas with solid magenta line (in two panels only) illustrate how the model fit fails if the ζ term in Eq. (3) is not included.