Just my thoughts...
I've lived in and decorated several homes that had the shared wall issue. I've dealt with it in two ways.
1) paint all communal walls a neutral suburban beige and all room-dedicated walls a bold color.
2)built a wall build-out thing at the point where I wanted the room separated and painted both rooms individually.
Our last house was a split entry type of thing where our dining room and living room shared a long common wall. Hubby built out a wall, about 10 inches, at the point where the two rooms met. This made somewhat of a very large doorway into the dining room and allowed me to paint the two rooms completely different colors without it looking odd.
Our current house, all but the bedrooms, have all but two of the walls sharing with some other room, AND the entire floor plan is visible from every other point. I painted the entire house in a boring suburban beige and then painted one long wall in the dining room a dark brown, two walls of the living room a sageish green, and the box over the kitchen cabinets orange. The colors are all drastically different, but combine in that '70 avocado green, harvest gold, brown sort of way. (Link
to the declutter thread where I've posted pics.)
Because you have dark furniture in the DR, I wouldn't make the same mistake I did with using a super dark color on the walls unless you have massive amounts of sunlight to combat the darkness. You seem to have a denim blue kind of thing going on, and yellows will really compliment that. Yellow can lead to using an orange in an adjacent room.
Just remember that paint is never permanent, you can always paint over it if you don't like it. Be bold with your color, you can always tone it down later. Also, when choosing a dark color, complete the entire wall with all coats before you freak and decide that you hate it. I LOVE my bedroom paint color, but almost nixed it after the first coat on half a wall.
Without knowing you, your style, or having seen the home; it's really difficult to offer up more than what I have. You may not be dark and bold paint color people, or you may have a formal feel to your homes, or a very relaxed feel. You may enjoy light breezy type decorations, ....hrm, which would look good with the blues.... Sorry, sidetracked. LOL
I'm rambling, but I just love paint! LOL