Saw some swallows or swifts yesterday, but I couldn't tell which at the distance they were.
You’ve no real hope of seeing the difference on the wing (ie colours and so on) They do move differently, Swifts are much stiffer in the wings, and also generally fly very high. The best way to tell is to listen. Swallows chat, Swifts scream (and Housemartins blow raspberries)