G−J vs. G−G _RP diagram at the low-mass end. The open triangles show previously known objects found in Gaia DR2 (see Sect. 2). The dots show the filtered Gaia DR2 catalog with a 2MASS counterpart and a 2MASS photometric quality flag Q _fl = AAA, before (left panel), and after (right panel) removing objects with an RP/BP flux excess following Evans et al. (2018). The curve shows the empirical limit we used to filter objects with spurious colors.