As the name would suggest, color is the dominant element of a color-field painting. It's the subject of the painting, and the point of the painting. There isn't anything to worry about "getting" or "understanding", it's about the sheer beauty and impact of color on your sense and emotions.
The "field" part of the name "color-field painting" makes me think of agriculture. Those vast sweeps of grassland or golden wheatlands where the color shifts gently as the wind blows through the crop. The beauty of a color-field painting is similarly in its shimmering shapes of color, the filling of your senses with color as you stand in front of it. Shape for the sake of shape. Color for the sake of color.
"...abstract art does not employ subject matter that is obvious as either the anecdote or familiar objects, yet it must appeal to our experience in some way. Instead of appealing to our sense of the familiar, it simply functions in another category."
-- Color-field Artist Mark Rothko, in his book The Artist's Reality: Philosophies of Art, p80.
