(i−J vs. J−K) colour–colour diagram for candidates with optical spectra. Symbols are as follows: sdM/L (filled red squares), esdM (filled green circles), usdM (filled blue triangles), candidates with uncertain class (filled black upside down triangles), and solar-metallicity M dwarfs (filled black diamonds). The empty five pointed stars represent the 14 candidates without optical spectroscopy yet. We also included a few known subdwarfs, extreme subdwarfs, and ultrasubdwarfs published in the literature (empty symbols). The empty diamonds joined with a continuum line in the right part of the diagram are solar-metallicity M dwarfs from West et al. (2008). The J and K magnitudes of candidates with ID = 1–29 are in the UKIDSS Vega system (Hewett et al. 2006), except for objects with ID = 1, 2, 6, 10, 11, and 19, which are plotted with their original 2MASS photometry.