The Blues are Paul Opler's specialty. He's been finding the differences in the species, using not only the visual butterfly, but comparing genitalia, foodplants, local populations, and some dna work. This one was pointed out to us by Paul as E. intermedia.
One way to tell the difference between genus is that Euphilotes have gray/black spots that don't shine, outside the orangs spots. Plebejus have silvery/blue irredescent spots.