Density map of the difference between mean ASAS-SN V and mean Gaia G magnitudes versus Gaia G_BP − G_RP colour for all ASAS-SN sources with a Gaia DR2 ID provided in the ASAS-SN catalogue. A random number between −5 and +5 mmag has been added to V to smooth out the two-digit precision magnitude published in the ASAS-SN catalogue. This is not necessary for the Gaia magnitudes, which are reported with four digits in that catalogue. The solid line represents Eq. (7) as a function of G_BP − G_RP, and the two dashed lines represent deviations of 0.5 mag above and below this function. The axis ranges have been limited for better visibility.