Color can sometimes confuse and squinting helps to limit color so that light or dark value can be seen. Check to see if the corners and edges seem incomplete. If they are not well painted, it will impact on the entire painting. Make every inch of a painting just as important as the one next to it. Find a particular color and see if it exists in more than one place.
Color can create or confuse a composition.
By repeating a color in several places throughout the painting, one can create a more cohesive composition. This is called Repetition of an Element and can be done with line, form, or color.