I live in a big open space, and I think one color flows better than deciding where the dining room starts and the kitchen ends with a change of paint.

YES, totally weird... :)

My home is exactly the same way. I ended up going with one color. I thought about trying to paint rooms different color and decided against it. I think it would very odd. It would make things look choppy and ruin the open concept and the feeling it has.

Another option would be to just paint one of the walls a color and do the "feature wall" look. I would not get too carried away with this. I would do it just in one room.

Pretty weird. I should know, since I just did it. :) The areas aren't totally open to each other; from the entry way one can see the living room and dining area, but the kitchen is hidden from the entry by a wall. The kitchen and dining area are open to each other, so you can see the kitchen from parts of the living area.

I'm not convinced I love it yet, but since I still have trim to paint and the house looks like it exploded, it's staying put for now.

I painted the living area a light blue color, and the entry way and dining area a darker blue color. I separated the two colors with a strip of the white color the trim will be painted.

I justified it to myself that the entry is sort of tucked into an alcove, so the transition between colors is only on one wall. The larger transition is from the living area to the open dining room, but it's only on one wall as well since the kitchen is separated from the living room by a wall. There will be another transition between the dining room and kitchen, but there are cabinets there so the transition should be a little easier to hide. I'll deal with that when I decide what color I want to paint/stain the cabinets and what color to paint the kitchen walls.

I think the transition would work better if I could find some sort of sconces or metal artwork narrow enough to fit on the white transition strips to pull them all together, but maybe not.

It would just seem more choppy. I have a condo that has a great room with angled walls and I painted it the same as the kitchen. It seemed easier and I wanted everything to flow. Maybe you could pick one wall to be different but it would be easier if you showed pictures. A big colorful piece of art might be an easier way to go and add color to an area. See the post someone has about art over a fireplace. Its big and I didn't get the feeling it was very expensive unless you have alot of art and perhaps could place it where you want the color on the walls.

That's one way you can define a different space in an open floor plan. It can be choppy but I couldn't really offer up opinion until I saw the space.