I've had a pair of navy suede string loafers that are a few years old (purchased when Epaulet dumped their remaining stock - however long ago that was) and mine are decidedly navy. As often stated, there are always inconsistencies in colors from batch to batch. If unworn, you can contact seller and ask if they have a "lighter" pair you can exchange for. Perhaps leaving them in the sunlight will lighten them a little bit.
9/23/16 at 8:12am