Eagle-eyed Flickr user Mike Ryffranck posted this a couple of days back, highlighting that apparently LEGO made the hair for generic hero guy #3 in Star Wars Rebels (or, Kanan) black instead of brown. The change goes beyond the hair, as well, as the goatee and eyebrows have also changed color on the face.
I guess they’ve either noticed the oversight, or more likely a few people complained about it and they’re working to fix it. Your mileage may vary, but if you’re concerned about the hair, you can try to contact them, but per Mike, they are currently backordered. I’d expect them to be fixed in the next production run of The Ghost (if it hasn’t been done already, since the replacement parts are out there and can be purchased on eBay).
To be honest, I don’t care about the color (and hadn’t noticed), but I’m not one to turn down getting the right parts from LEGO. Guess it’s time to go fill out some customer service forms…