How Do I Bring Color into My Living Room? -- Good Questions

Q: I live in a practical but uncharming 70s house. It's great, since it provides much needed space for small and big kids, but we have been living here for a year and now I'm itching for color. The current interior is mostly wood (including more than a few things from IKEA :), with a white dining table and chairs, and a black leather sofa. And yes, there is beige/brown wall to wall carpet. Should I plan to paint just one wall, or the whole space? Punchy or sophisticated color?