Now think of a room that is bright yellow and blue. Looks like a fun room but it does make you look at what's in the room rather than just being in there with lots of elbow room. Both rooms can look good; the point is they each create their own visual space or lack thereof.
If space is something that needs to be visually expanded, then there are other tricks besides using color saturation. For example, small, square rooms will do well if two opposite walls are painted the same color, preferably an intense one. The deep color will create a feeling of depth, therefore opening up the room.
A deep, deep ocean is seen as dark water. The feeling of depth and great expanse is there even though the water is right there where we can touch it.