The living area, dining area and eat in kitchen of my new home are all very open.
I knew that I didn't want all of the walls the same color so I used the colors in my oriental rug to tie them all together. Without this inspiration piece, I'm afraid I would have made a mess of things.
The walls in the foyer are dark red, the main living area is a neutral stone gray, the kitchen a soft mossy gray-green and the dining room is mustard yellow.
All of the rooms have white wooden ceiling and floor molding that makes it all (as you say) flow.