Comparison of PARSEC metallicity isochrones of −3.0 and ages 8, 12, and 14 Gyr with the position of the stars in the colour-magnitude diagram. The colours (Bp−Rp)₀ and the G₀ magnitudes of the stars have been computed from the Gaia-DR2 photometry. The stars of our sample are represented by black dots, and the Li-poor stars (stars that deviate by more than 2σ from the Li plateau) are circled in red. The three Li-poor stars from the First Stars sample (green dots) have been added.