The afterimage created by blue, which is a faint orange, will overlap onto the nearby orange and make it seem brighter. And at the same time, orange's afterimage, a faint blue, will overlap onto the blue and make it seem brighter. By placing the powerful blue next to the orange, Frankenthaler was able to create enough visual interest to pull the eye up and away from the yellow, thus creating a very successful painting. Rather than simply letting its shapes form something familiar for me to recognize, I try to keep focused on the elements of the painting and the atmosphere that they generate together. That is the point of this particular form of painting.
Realism takes it easy on our brains by making things obvious.
Abstract art is more demanding on us for understanding. The force is not in the form. It is what the colors invest in the form that is important. I don't have to pursue it. I know it.