As of February 13, 2013, Great Smoky Mountains National Park requires a permit and reservation for all backcountry camping in the park. Prior to that only certain campsites required reservations and those were designated on the Trail Map and Guide with red (technically, magenta) numbers. The others were shown in green. In the list of the campsites on the reverse side of the map, bold type was used for the names of the site to designate those that required reservations.
The new October 2012 Park Trail Map now uses magenta to designate a "Hiker only campsite" and green for a "Horse and hiker campsite." On the reverse side of the revised map a bold H designates those at which horses (and other pack animals) is allowed. (It is not clear why the "H" needs to be in bold type.)
It is not necessary to count my teeth to verify that I am a mere 2 years and 22 days away from being 70 years old. So I maybe have an excuse. But I can't help but think even younger backpackers will be confused with the recycling of the use of red and green and bold type.
To help us in the transition to the new reservation system and to avoid mistakenly hitching our horse up at the wrong place, I plan to suggest to Great Smoky Mountains Association and, if necessary, National Park Service leadership the use of pictographs similar to those pictured below. We are using those to update our maps. To my knowledge there is no official NPS symbol for "no horses allowed," just the one used for "no horses allowed on certain trails" (see photo).
Okay... there are at least two hitches that come to mind that would need to be plowed through: 1) the size and scale of the Park map would not easily accommodate the use of my jumbo-sized "no horses allowed at this campsite" symbol and 2) the NPS cartographer appear to have to adhere strictly to the use approved pictographs only.
One solution regarding the first hurdle would be for the NPS to produce a slightly larger map and charge say $5 (plus a free PDF download) to take its place. The current map is $1. (We have been including the Park Trail Map for free in the printed fishing map sets we sell, but that might have to change.). If the enlarged map was designed well enough, I think most Park visitors wouldn't mind terribly inserting a fiver in the slot of honor system boxes.
Finally, I am planning to contact Trails Illustrated to see where they stand in revising their three maps of the Park.