(J−H) vs. (H−K_s) CC diagram drawn for stars (with A_V ≥ 1) from the region containing Gal 110-13 to illustrate the method. The solid curve represents locations of unreddened main sequence stars. The reddening vector for an A0V type star drawn parallel to the Rieke & Lebofsky (1985) interstellar reddening vector is shown by the dashed line. The locations of the main sequence stars of different spectral types are marked with square symbols. The region to the right of the reddening vector is known as the near infrared excess region and corresponds to the location of pre-main sequence sources. The dash-dot-dash line represents the loci of unreddened CTTSs (Meyer et al. 1997). The open circles represent the observed colours, and the arrows are drawn from the observed to the final colours obtained by the method for each star.