For me, the answer is three, at least that's how many times I've repainted my living room wall in the past month in my (seemingly endless) struggle to find the perfect color.
Round 1: Inspired by the blue walls at the RISD Museum, Liberty of London, and a Cape Cod living room designed by Marcel Breuer, I boldly took up a paintbrush with Behr's Royal Peacock and loved the result for the first five minutes, until I realized that, oopsie, it's pretty much the exact color of the painter's tape … and the bag The New York Times comes in … and every generic blue plastic object my toddler lugs around the house … you get the picture.
Round 2: Still in love with the bright blue idea, but not the exact bright blue I had chosen, I tried Benjamin Moore's Seaport Blue with hints of green and moved the gray couch away from the wall. The result? Better, but not quite there yet (and not enough of a difference from the first blue).
Round 3: I finally opted for the exact shade used by the RISD Museum in their European Painting Gallery, A New York State of Mind by Benjamin Moore. It was a big change from the first two, but feels much more sophisticated. I'm not sure yet if I love, love it, but I'm now too exhausted (and officially forbidden) to paint the wall again—at least for a month or so. I guess we'll see what happens.