Theoretical and observational color-magnitude diagrams. Left panel: Gaia EDR3 color-magnitude diagram. Newtonian and general relativistic cooling sequences are displayed using cyan and black lines, respectively. Their rest masses are, from top to bottom, 1.29, 1.31, 1.33, 1.35, and 1.369 M_⊙. The Gaia white dwarf population within 100 pc is displayed using gray dots. The faint blue white dwarf branch reported in Scholz (2022) is displayed using large red filled circles. Dashed lines show isochrones of 0.25, 0.5, 1, 2 Gyr. Right panel: zoomed-in view of the faint blue white dwarf branch. Objects {j, s} (marked in blue) are ideal candidates, compatible at a 1σ level with the general relativistic model but marginally at a 2σ level with Newtonian models.