We have a saturn coupe thats been sitting for about a month or two and
when i went to check the oil i noticed brown sludge around the coolant
container. I opened it and it seems to be full of this light brown sludge. i
don't know if it is really full as i didn't go digging into it but it looked like it.

Any advice?

The coolant resevior is known to getting dirty. The only thing you can do it take it out and clean it

Yeah, clean it out and see if it comes back once you fire the engine up.