J − H, H − K colour–colour diagram of W49 for only the 22 sources discussed in the paper. The late type stars are not included here. The symbols have the same meaning as described in Fig. 2. The two black dashed lines represent main sequence isochrones with the age of 1 Myr, and the initial mass ranges from 0.8 to 500 M_⊙ from Ekström et al. (2012) and Yusof et al. (2013) without being reddened (bottom left) and being reddened with A_Ks = 5 mag (upper right). The red diagonal line represents the reddening law according to Indebetouw et al. (2005).