The coloring of the Lyside Sulphur varies. The upper side of the wings is pale yellow. It usually has a black bar on the top edge of the hind wing (the bottom wing). There is normally a bright yellow patch near the base (where the wing connects to the body) of the fore wing (the top wing). Some individuals also have black borders along the top edges of the fore wing. The underside of the wings varies. They vary from a greenish color to bright yellow to almost white. Greener individuals have a whitish vein in the center of the hind wing. The fore wing has a bright yellow basal patch. The wingspan is 1.5 to 2.38 in. (3.8 to 6 cm.).