If the impact is big enough, the resulting worldwide earthquake and volcanic activity would destroy the colony, surface or underground. Given underground colonies _rely_ on equipment just to stay alive, the destruction of this equipment would have greater damages than surface colonies. Then, if the main power source of an earth underground colony is solar power, then they would not end up much better than the surface one. Getting closer to earth core as seismic insulation and power source may or may not solve the 2 problems mentioned above.