Most hunters in the US wear a blaze orange vest or hat to identify themselves to other hunters. In some states it's codified by law, and in others it's strongly encouraged (in California it's a big part of the mandatory hunter safety course, but is not legally required).

Many big game animals are color-blind (or more specifically, see color differently than we do), so a camo pattern with orange can still hide one from a deer, while making you visible to humans.