H − K_s vs. K_s −[3.6] of the IR-counterparts with measurements in the H, K, and IRAC channel bands. the solid square corresponds to the central C-HII region E, the asterisk to source #43 in region F. The rest of the symbols are as in Figs. 3 and 4. The solid line close to the origin represents the locus of the main sequence (Koornneef 1983) and the dashed line represents the reddening vector of length A_V = 35 (Tapia 1981).