The technology for that colony would also be applicable to underground vaults, or we could first build those.

Either way, events such as these that would have wiped out humanity as it exists today have not yet happened in the ~1.6 billion years of eukaryotes existing on Earth, so there are good reasons not to worry too too much about it.

Note that the asteroid that "wiped out the dinosaurs" would still have left humanity as it exists today in a much better shape than a Mars colony is likely to ever be in.

Also, note that much smaller meteors/asteroids pose a huge risk to a Martian colony than they do to Earth, as they burn less in the almost non-existent Martian atmosphere, and since a Martian colony will be much less geographically spread out than the Earth. An asteroid wiping put all of the people in North America would still not destroy life on Earth, while a similar impact would easily destroy any human life on Mars for any kind of foreseeable future, if it happens to hit the colony itself.

On the other hand, due to basically no hydrosphere and very thin atmosphere, there would be much less shock waves, no trees to burn, no post-impact winter and a lot of the ejecta might end up in space due lo lower gravity. instead of falling back to bombard the planet.

So certainly a bad news for the one spot, but another outpost a couple hundred km distant could be fine.