The Golden-Winged Skimmer, the female Great Blue Skimmer, Needham's Skimmer, and the female Slaty Skimmer are very similar in appearance. to the Spangled Skimmer. The distinguishing marks are the white pterostigma.

"Spangled refers to the flashy white stigmas." (Dunkle, Dragonflies through Binoculars, p. 178)

This is another view.