Ihave used it for many years and it doesn't leave any color or residue on your fabric. I cut my thread, run it into the beeswax and thread the needle with the end in your hand as you cut it off the spool.
Works good for rubbing on drawer slides or table top slides too, just rub it on.
Beeswax candles, unless they are sold as pure 100% beeswax, might have paraffin or perfume in them, I wouldn't use one.
Carol J.