The Orange Sulphur (Colias eurytheme) is another popular sulphur butterfly that is widespread in Maryland.
Much of the same logic applies to these sulphurs, you have no idea which one your seeing with the naxed eye, unless you can catch a top view of its wing in flight. What I will say about the Orange Sulphur, is, it is visibly more striking than the clouded sulphur in flight.
The Orange Sulphur’s bright coloring on the tops of its wings and the hard black outlines each stand out as the wings flap. I managed to snap the photo to the right while this species was in motion, at Idylwild Wildlife Management Area, and you can see the coloring is incredibly strong.
At rest, the wings are always closed, so your best bet if you want that flash of color, is to just hold a continuous-shot mode on the butterfly and wait for it to take off again. It moves fast and usually does not linger long at a particular plant.
Besides the top wing coloring, the distinguishing characteristic in the Orange Sulphur is in the arrangement of its underwing specks, as compared to other species found in Maryland. Five distinct marks can be seen arching around the wing’s white eyespot, as opposed to the three or possibly four marks visible on the clouded sulphur, or the complete smattering on the Little Yellow and Cloudless sulphurs.