I use a combination of yellow or orange duct tape. My red based carries have yellow around them, the rest is neon orange. Because a lot of the interior of my packs are black or I might be trying to find the object at night with flashlight, I tend to put patches of neon orange on gear I need but might be hard to find.

Btw, I also put orange duct tape on the back of my tv remote. It always seems to be face down when I am looking for it, so that neon color really pops on my furniture.