I've used/seen a number of effective methods:

One of my sons wrote his first name on a black canvas bag with white out.

I use a fluorescent orange bag tag, yellow FT Priority tag and fluorescent green luggage strap on my black/blue bags.

Mrs BamaVol and Gramma Bama tie colorful scarves on the handles of theirs.

Another of my sons uses a rainbow luggage strap I picked up in London - the rainbow is grey, purple, yellow, blue & orange - not at all the usual rainbow strap you see here in North America.