Spectral-typing indices TiO 2, TiO 5 (top), PC1, VO-7912 (middle), Color-M, and Ratio B (bottom) as a function of Hα pseudo-equivalent width for spectral types M3.0 V, M3.5 V, M4.0 V, and M4.5 V, from top to bottom. For clarity, the indices are offset in steps of 0.1 in the vertical axis. Solid lines are linear fits of the indices as a function of pEWH(α). Dashed lines indicate the mean and ± 1σ index at quiescence (pEWH(α) > –1 Å).