Oil paint
Color field, curiously enough or perhaps not, became a viable way of painting at exactly the time that acrylic paint, the new plastic paint, came into being. It was as if the new paint demanded a new possibility in painting, and the painters arrived at it. Oil paint, which has a medium that is quite different, which isn't water-based, always leaves a slick of oil, or puddle of oil, around the edge of the color. Acrylic paint stops at its own edge. Color field painting came in at the same time as the invention of this new paint.