A single saturated wall is the cheapest way to give a room a centre of gravity. It is also the easiest thing to get wrong.
Choose the wall you already look at
The wall behind a bed, sofa or dining table is already the focal point of the room. Colour there reinforces the layout instead of fighting it.
Keep the other three quiet
An accent only works against restraint. Keep the remaining walls in a neutral from the same family, and let the trim stay white so the transition is deliberate.