Gravity-sensitive spectral index γ as a function of T_eff for the sources (open squares) in the field of the SFR Cha I. The candidate members of Cha I are marked in red squares, while the other coloured squares denote the field contaminants of interest: Li-rich giants (blue), (non-Li-rich) giant outliers (fuchsia), NG non-members with Li (green), and potential NG outliers (turquoise – i.e., those in the 1.01 >  γ >  1.0 range, see Sect. 4). As indicated by the dashed lines, we classified any stars with T_eff <  5200 K and γ >  1.01. as giants.