Without rules you can't have anything, but you don't want to just be pedantic or obsessive. The painting is finished when it's working. The overall balance is right. Balance shouldn't be confused with design. There has to be restless jostle and aggression and a bit of dynamism, not just pat-ness or settled-ness or immediate pleasing-ness.
Until the late 1970s there'd either be only black or white in the paintings or if there were colours it would be a small amount, not a large area, and with the color separated from other colors by black or white (which is formula for Damien Hirst's successful dot paintings, incidentally).