You can buy all types of very strong and brightly colored tape at any hardware store and many stationary stores, just don’t tape over the zippers where airport security may have to remove the tape should they want to inspect the contents of your bag.

You can buy different colored electrical tape and tape the handles of your luggage.

You can buy this tape at any hardware store

Buy colored duct tape at any hardware store.

A name tag that stands out in some way. My friends used to use something with neon colors or a wacky design.

I use stickers on the smooth places, where they’ll least likely rub off; use several.
my son ties white elastic on both sides of handle.
Polka Dot spray paint would probably be unique. [vinyl shoe paint]

buy the most odd looking and ugliest luggage there is that should do the trick..

Get something out there on your suitcase like a big sticker,
or even just buy a bag thats a bold colour?

I think a ribbon will do fine. Just tie it tight and make sure it is a distinct color.

colored duct tape