Isochrone fitting for NGC 2425 with Gaia DR2 data. The PHOENIX and ATLAS9 models, and a smooth transition between the two are used for (G_BP − G_RP)₀ ≳ 0.94, (G_BP − G_RP)₀ ≲ 0.55, and 0.94 ≳ (G_BP − G_RP)₀ ≳ 0.55, respectively. For simplification, we fix the metallicity ([Fe/H] = −0.15 dex) and the true distance modulus (12.644 mag) as that derived from Bossini et al. (2019) for all the isochrones. The red solid line and blue dashed line are best-fit isochrones with variable extinction coefficients based on Fitzpatrick & Massa (2007, FM07) and CCM+O94 extinction laws, respectively. The vectors represent the corresponding fixed extinction coefficients. The green dot-dashed line is the best-fit isochrone with fixed extinction coefficients based on FM07 extinction law. The black dotted line shows the isochrone of the same age and metallicity as that of the red solid line, but with the extinction coefficients from that of Bossini et al. (2019).