Cumulative distribution functions for the GCNS background distribution (dashed blue), the V-LoTSS × GCNS sample (green), the LoTSS × GCNS sample (orange), and the VLASS × GCNS sample (grey), shown as a function of Gaia colour G_BP − G_RP. The top panel shows the two radio-detected populations with the inclusion of chromospherically active stellar (CAS) systems. The bottom panel shows the population without them. The shaded regions correspond to the 95% confidence level based on a binomial distribution. As the number of sources in GCNS is much larger than the radio-detected populations, the confidence interval of GCNS is negligible. The top axis of the CDF plots indicates the nominal stellar spectral types (Pecaut & Mamajek 2013).