Comparison between the radial distribution of UV-blue (continuous blue line) and UV-red (dashed red line) for all the considered clusters. The data within the radius marked by the dotted lines in the plots of the distributions for M 53, M 2, and M 13 were not included in the analysis (see Sects. 2 and 2.1). See Table 2 for the significance of the detected differences, as measured by the KS test.