Very good points! Keeping track of companions is a good reason to wear easily visible colors. This is especially true if you take small children on outdoors trips. Obviously it is good to be able to to see your kids. It is also reassuring to them when they can easily see you.

Regarding gear, we once lost a perfectly good set of trekking poles ( dark colored). My wife had collapsed them to the storage size when we got down onto an easy trail, and was carrying them in her hands. At one of our rest stops at a nice grassy spot we sat down and she laid them on the ground, while we had a snack. When we got up to move on she forgot to pick them up, and we walked several miles before we realized we did't have them. Since then I've marked most dark or small items with bright orange tape or cord etc. It makes it much easier to spot them with a quick scan around the area when you move on.