I think colonists' should play music, its as simple as that. Of course they won't be able to play it as loud as the player so it won't get too annoying but I think this would be a nice touch. (Talking to them would stop them from playing) If possible you could have a separate music list where that's the only music a colonist can. So if you only want them to play one song and that song is your colony anthem then so be it! Not much as I can say or add for its pretty self explanatory.