J − H vs. H − K_s diagram of the near-IR counterparts with measurements in the three bands. Solid circles are sources in the dark cloud west of the HII region D. Solid triangles correspond to sources within the limits of CNN. Open squares are in region I(N). Open circles are for sources in the rest of the observed field. The solid line marks the locus of the main sequence (Koornneef 1983), the dashed lines delineate the reddening band for all main sequence star and giant stars (Rieke & Lebofsky 1985). The small plus sign near the bottom of the plot illustrates the maximum photometric errors.