Added a link from the Info page to this sighting, since David Ferguson gave a good explanation about distinguishing white-form Orange Sulphurs.

Moved from Butterflies (excluding skippers).

Moved from ID Request.

however, I'll try. In the Clouded Sulphr the wings are usually slightly narrower with the angle at the tip of the forewing a little more acute. The underside, especially on the hind wing, usually has distinct fine gray scaling that tends to give it a bit of a gray or greenish tinge. On the upper side the dark border (showing through from above here) is usually narrower, and more interrupted by pale patches on the female hind wing. The orange vs. yellow color above usually works fairly well, but obviously not on a white form female (or rare white form male).

Notice that everything above is qualified with a usually. The two overlap in characteristics, but the total picture usually makes them fairly easy to tell apart. However, some individuals, especially from very early or very late in the season (or winter in the South) can be very difficult to identify. The ultraviole reflective pattern on the upper surface is different too, but that doesn't help much here. Also, some intermediate looking individuals might be hybrids (this one doesn't look intermediate).

Even though a bit wishy-washy, I hope that helps.

of Orange Sulphur - Colias eurytheme