Right place for editor css?

Hey guys, I’m going to be changing the bbPress editor color scheme to work with a dark theme, and I’d like to know where the correct place is to do this? Where is the original css for the editor? Where would I put the “child” css? (if it’s different than the css folder in my theme)

I’ve been searching the forums, ‘net and files and can’t find it, so any help would be greatly appreciated.

I’m using the most recent versions of WordPress, bbPress and BuddyPress.