J−H/K− [4.5] diagram for the sample of 2116 sources with photometric errors <0.2 mag in these bands (black dots). The already classified YSO candidates are shown with red squares (Class I) and green circles (Class II). The location of the bright sources A, B and C, of which A and C are resolved doubles in the near-IR, are marked with blue stars. Some sources have upper limits only in the J band. Some have lower limits due to saturation in the 4.5 μm band. The slope of the reddening band is indicated as a dashed line.