You can use different colors in each room, but if rooms are attached to each other, the colors should flow from room to room.
For example your living room may have dusty blues, creams and a touch of pale yellow. The attached dining room may be sage green also with pale yellow and perhaps a touch of dusty rose, thereby pulling the colors along from room to room. You want a graceful flow, not a choppy seperation.
If your floors have carpet or tile, look closely at the colors hidden in there. Are there specks of color in the carpet? These little hints of color can help you in choosing your color scheme and in creating that graceful flow of color.
Even if you don't own your home, you can now add color to any room or any wall with the new stick and peel wallpapers. These wallpapers can be put on any wall and then when you are ready to move, they just peel off. No glue or paste so no steam or residue. They are available at large hardware or decorating stores (Think Lowes, Crate and Barrel) in a variety of colors and patterns. These stick and peel papers aren't cheap, but if you are only covering one wall, you will cut down on cost and add color to your room.
Keep in mind, no matter what colors you decide on, you are the one living there - so you are the one who has to like it - not some designer that thinks everything has to match, or some designer that thinks nothing should match. Whatever you decide, make it what you like it.