RS parameters vs. redshift: the (r′ − i′) vs. r′ slope (upper panel) and (r′ − i′) color at r′ = 17 (lower panel). Black symbols indicate DARC clusters and red symbols indicate relaxed clusters. The solid line in the upper panel shows the mean value for all ten clusters. The solid line in the lower panel shows the linear fit. The dashed lines show one-sigma uncertainties of the linear fit.