https://www.wideopenspaces.com/know-use-purple-paint-posts-trees-texasPosted by Craig Raleigh
There are multiple states in the U.S., including Texas, that use the color purple as a warning to trespassers.
Purple shows well in the outdoors. In fact, it's one of the only colors that colorblind people can easily identify. Having said that, just seeing it on a fence post or painted on a tree as you go by might only garner a quick glance and an odd look.
It started in Arkansas in 1989 and by 1997, Texas had adopted the "purple paint rule" as an act of legal legislation to post private property. Not only does it mean "no hunting," it also means "no trespassing," and is an effective way for property owners to post their land quickly and easily.
As Jonathan Kennedy of EastTexasLands.com says in the video, "The reason they did that is they were trying to keep landowners from constantly having to replace signs."
https://youtu.be/-_OetOA7qOsOriginally landowners were required to have a "no trespassing" or other sign posted to explain the purple paint, but only one year later that rule was rescinded. The new law states that the purple paint marks must be located in vertical lines a minimum of 8 inches long and at least 1 inch wide.
The marked posts or even trees must have clearly visible paint and that paint must be placed 3-5 feet from the ground. Other states with purple paint rules to indicate property lines include Kansas, Arizona, Montana, Arkansas, Idaho, Florida, Maine, North Carolina, Missouri and Illinois. Pennsylvania also recently adapted the use of purple paint markings to indicate no trespassing in 2020.
No matter what state you're in, "posted" and other no-trespassing signs can be a headache for landowners to constantly replace. The purple paint law makes things a little easier, both from a maintenance standpoint, and on your wallet since you are not constantly replacing worn and broken signage.
Now we just need more states to get in on the purple markings rule. It seems like it would make criminal trespass and other law violations a lot easier for law enforcement to police. The only thing left to be done is to share the meaning of the rule so everyone knows!