CaT region of the normalized spectra (Sect. 3.3) for three stars within the field m 0.7 m 1.4. Vertical cyan lines mark the position of the three CaT lines. The top and middle panels show the two stars marked as blue (top) and red (bottom) dots in the CMD shown in the left panel of Fig. 2. Their position in the CMD and the strenght of their CaT lines suggest that they are metal-poor and a metal-rich star, respectively. The bottom panel shows the faint star marked as a black dot in the left panel of Fig. 2. A gray shaded area shows the flux error in the three panels, as estimated from the magnitude errors provided by DAOPHOT. Due to the different SNR of the three spectra (shown in the figure labels), the gray shaded area is only visible in the bottom panel.