It really depends on you the home owner and what you would like to see each day. It is certainly much easier to paint it all one color. Although I would prefer to have a few different but similar colors. Like have the kitchen an eggshell, hallway off-white, and bathroom maybe a light tan. This doesn't make the bathroom to dark and allows for some light saturation through the windows. The hallway is a neutral area and is not a main focus. So an off white would suit this area. The kitchen is a common area and eggshell is a common color used by many paint contractors. You can certainly go outside of the box and use some brighter colors for the kitchen. But I think keeping it simplistic is the right way to go.