Left panel: (J − K,K) near-IR colour − magnitude diagram of the 2MASS counterparts of our X-ray sources. The main-sequence (from Knödlseder 2000) is shown for a distance modulus of 10.4 and for two different values of the reddening (from left to right, A_K = 0.0 and 0.78, Bica et al. 2003). The reddened pre-main sequence isochrones from Siess et al. (2000) are shown for ages of 2 and 3 Myr (dashed lines). Right panel: (H − K,J − H) colour − colour diagram of the 2MASS counterparts. The solid lines yield the locus of the main-sequence according to Bessell & Brett (1988), while the dashed straight line indicates the locus of the unreddened classical T-Tauri stars following Meyer et al. (1997). The reddening vector is shown according to Bica et al. (2003).