French onion soup has a pretty dark brühe colour normally, so that isn't that weird. (no clue how to say brühe on english, maybe broth is the right word?). Though this one is very dark, but that might be because of the amount of caramel / other colourants added.
But, if it's a bad smell.. I suppose it went bad. Because it has to smell like baked (not raw) onions instead. And I think we're all very familiar with that smell.
Quite strange in my eyes though, dehydrated onions are not that easy to spoil.. Even raw onions can last 6 months without problems. Add a lot of salt to that, and then freezedry it, and pack it in an controlled atmosphere. That should garanty quite some shelflife in my eyes.
It might be stored in bad conditiosn in the past, because you never know where rations have been in their life, and how they were stored.
A shame though, it seemed to be a nice appetizer. I actually like onion soup alot..

Sure, someone may one day kill me with my own gun.
But they'll have to beat me to death with it because it's empty.
A computer once beat me at chess, but it was no match for me at kick boxing.