Colour (J − K_S) vs Spectral Type diagram illustrating distribution of our targets in terms of colour anomaly. Black points show 203 brown dwarfs in the L/T transition gathered by criteria from the SIMBAD database for various SpT, with the median colour shown as a grey star for a given SpT (size proportional to the number of BDs in that bin). J2139+0220 is included for reference as it is very strongly variable and has been shown to inclined at 90°. Detections and non-detections are shown with J − K_S error bars in dark red filled and purple empty circles respectively, with the marginal detection of J2148 shown as a combination of the two. Poorly constrained 2MASS K_S photometry for J2148 and J2239 is indicated by upper limit arrows.