  Color centers in diamond have emerged as leading solid-state artificial atoms
for a range of quantum technologies, from quantum sensing to quantum networks.
Concerted research activities are now underway to identify new color centers
that combine stable spin and optical properties of the nitrogen vacancy
(NV$^-$) with the spectral stability of the silicon vacancy (SiV$^-$) centers
in diamond, with recent research identifying other group IV color centers with
superior properties. In this Letter, we investigate a new class of diamond
quantum emitters from first principles, the group III color centers, which we
show to be thermodynamically stable in a spin-1, electric-field insensitive
structure. From ab initio electronic structure methods, we characterize the
product Jahn-Teller (pJT) effect present in the excited state manifold of these
group III color centers, where we capture symmetry-breaking distortions
associated with strong electron-phonon coupling. These predictions can guide
experimental identification of group III vacancy centers and their use in
applications in quantum information science and technology.
