Scully's paintings are often made up of a number of panels and are abstract. Scully paints in oils, sometimes laying the paint on quite thickly to create textured surfaces. Today he is one of the most widely acclaimed and exhibited painters in the world. After a brief initial period of hard-edge painting Scully abandoned the masking tape while retaining his characteristic motif of the stripe.
For over a quarter of a century since he has developed and refined his own instantly recognisable style of heroic geometric abstraction. His paintings typically involve tough architectural constructions of abutting walls and panels of densely and lushly painted stripes.
Though he frequently works on a monumental scale, even on a more modest scale his paintings and works on paper exude a romantic gravity of an unmistakably urban rather than rural tenor. In recent years he has augmented his trademark stripes by also deploying a mode of compositional patterning more reminiscent of a checkerboard. He has stated that this style represents the way in which Ireland has moved towards a more chequered society. He stated in 2006, "I remember growing up in Ireland and everything being chequered, even the fields and the people."