Residuals from the Güdel–Benz relationship vs. Gaia G_BP – G_RP colour. For the sake of clarity, the V-LoTSS × GCNS sample is omitted, as well as the two M dwarfs from the VLASS sample (grey circle) with residuals ≪10⁻³. They are LSR J1835+3259 and HD 43162C, with spectral type M8.5 and M5, respectively. The radio sources without a detectable X-ray luminosity are indicated with a downward-pointing arrow and are shown as 3σ upper limits. The top axis of the CDF plots indicates the nominal stellar spectral types (Pecaut & Mamajek 2013).