Dominance and Contrast

Deciding which side of the temperature scale is to be the dominant one in the painting is critical.  Throwing equal parts of warm and cool colors at the paper doesn't establish a clear color theme. But staying exclusively on the cool side or exclusively on the warm side doesn't provide enough contrast to create the tension that gives a painting interest. 

Think about a novel with a fictional character that is all good.  That would be a rather boring story. Most authors create interest in their good characters by showing a flaw in their character that leads to tension and therefore creates interest.  Their intentions are good, their past is filled with good decisions and actions, but suddenly a flaw crops up that contrasts with the dominant good side, and creates interest.

The same is true of paintings.  It is imperative that you know which temperature is going to "win" or dominate.  But it is also necessary to provide a touch of relief in the form of a cool at several places around the picture, especially near the focal point.

Here are two views of Hendrick's Head Lighthouse on Southport Island, Maine.