We extracted the peak vertical excitation energy from each of these calculations according to the following procedure: (1) if none of the energies were in the range of 1 -4 eV, choose the lowest energy; (2) if only one energy is in the visible range, choose that one; (3) if multiple peaks are in the visible range, choose the one with the highest oscillator strength. While the vertical excitation energy is not exactly analogous to λ max,abs because it does not account for nuclear vibronic effects, it is a relatively cheap computational surrogate that should improve the capability of a model to predict λ max,abs .