J − H vs. H − K_s color–color diagram toward Serpens South. The green and red curves indicate the loci of dwarfs and giants, respectively. The data for A0–M6 dwarfs and G0–M7 giants are from Bessell and Brett (1988). The blue dashed line denotes the classical T Tauri star locus of Meyer, Calvet, and Hillenbrand (1997). These loci are transformed to the 2MASS system by using the equations in the explanatory supplement (Cutri et al. 2003). YSO candidates are indicated by the red points. The black arrow shows the reddening vector of A_V = 5 mag. The three orange dashed lines are parallel to the reddening vector. (Color online)