We consider an excited-state manifold in which an allowed transition is strongly coupled electronically to a forbidden (dark) state and use nonperturbative methods to determine the effects of this coupling on the optical properties. We find that the strong coupling limit is qualitatively different from the usual weak coupling case; in particular, the bright state spectrum is substantially altered, displaying renormalized Franck-Condon factors which can be observed in absorption, hole burning, and resonance Raman experiments. We map out the magnitude of this renormalization as a function of various parameters in the theory and note that there is a phase-transition-like behavior as one passes from the weak to the strong coupling regimes. Finally, we suggest that this mechanism provides a straightforward explanation for the hole-burning spectra observed for the primary donor in the bacterial photosynthetic reaction center and determine a region of parameter space compatible with the experimental results.