Coombs: We might as well be wearing red shirts.
Coombs says this to Felger in an attempt to indicate the hopelessness of the situation (and that they'll die). The red-shirt reference is from Star Trek (mainly the original series). It is well known that in Star Trek, whenever an away team goes somewhere and there are some main characters in the group, there is always an extra couple of temporary characters who always wear red shirts. These are the expendables who always end up dying in that episode.