High quality paint on the entrance door will create an even color coverage. Whether it is a solid color or a color effect with texture, there should be no different shades of color, mottled or striped color differences.
Touch the surface of the entrance door. A good paint should make the door feel smooth, with no grainy, bumpy or orange peel texture. If there are obvious particles on the surface of the paint, it may be that impurities have been mixed in the paint construction process, or the paint itself is of poor quality and has not been fine-filtered.