(J − K)₀ colour histograms in 0.05 mag bins. Top: the distributions of the LP1 (red) and LP2 (black) samples. Middle: colour histograms for the spectroscopic sample presented here. The K- and M-type dwarf sources (black) and the C-type sources (red). A colour histogram (purple) for the spectroscopically confirmed M-type giants of Kacharov et al. (2012) is also shown. Bottom: as above for the sources classified as M-type (black) and the sources classified as C-type (red) in Catalogue 1 of Paper I. The dashed vertical line at (J − K)₀ = 1.20 mag marks the position of the colour boundary used in Paper I.