HR diagram of RSGs in NGC 6822, IC 10, and IC 1613 compared to RSGs in NGC 55 (de Wit et al. 2024). Four Posydon evolutionary tracks for Z/Z_⊙ = 0.2 are overplotted; the color indicates the central helium abundance, while dots indicate intervals of 10,000 yr. Each panel includes effective temperatures determined using the following methods: TiO-band fits (top), the i-band scaling relation applied to our TiO temperatures (middle), and the J-band scaling relation (bottom).