Don't get me started. The USFS and the state of Colorado, as well as other land management agencies, have agreed to use standard signs for roads and trails. But older signs are still to be found in the forests. I've asked the local USFS trails guy to replace these older signs with the newer standard signs but he says "... it takes time to change them all..." Funny how quick they can put up closure signs.
When you encounter a puzzling sign, take a closer look and read the fine print. Report any of these older signs to the local land management agency. And report any defaced signs also.
I'll track down the "official" sign standard and post a brief review here as soon as I get a few minutes of free time.