Whether you’re road-tripping through the countryside or hiking in an unfamiliar area, being aware of your surroundings is key to staying safe. One little-known but important visual cue that can help you avoid legal trouble—or worse—is the use of purple paint on fences and trees. Though it may seem decorative at first glance, these purple marks actually carry a serious message. Understanding what they mean and where they’re used can save you from accidentally crossing boundaries that land you in legal hot water.

Summer is a popular season for exploring. Families pile into cars for long drives, couples seek out nature trails, and adventurers of all kinds hit the great outdoors. Whether you’re camping, hiking, or just driving through rural land, it’s a good idea to be aware of property lines and local customs. One of the more surprising safety tips? Know the significance of purple paint. If you spot a fence post or tree trunk marked in purple, you should stop and take a closer look—because you could be unknowingly entering private property where you’re not welcome.

So, what exactly does purple paint mean? In several U.S. states, purple paint is a legal substitute for traditional “No Trespassing” signs. Landowners can use this color to mark the perimeter of their private property and make it clear that entry without permission is forbidden. While physical signs can fall down, be removed, or fade over time, purple paint is a longer-lasting and less vulnerable solution. It’s bold, eye-catching, and relatively easy to apply in multiple settings. This law is especially common in southern and midwestern states, such as Texas, North Carolina, Missouri, and Illinois, where rural landowners want a simple and inexpensive way to communicate property boundaries to the public.

This method of marking land is not only practical but also has the advantage of being more difficult to tamper with. Signs can be stolen or destroyed, but it’s far less likely someone will go to the trouble of painting over multiple purple tree trunks or fence posts. And it works—once people are aware of what it means, they typically know to steer clear.

Interestingly, purple is used because it’s one of the easiest colors to recognize, even for people who are colorblind. Shades of purple generally stand out in nature, making it an effective and inclusive warning system. It’s also visible from a distance, giving hikers, hunters, and off-roaders plenty of time to turn around before accidentally crossing into restricted land.

If you’re a landowner and want to mark your property using the purple paint rule, there are some very specific guidelines you need to follow. According to most state laws, the paint must be applied in vertical lines that are at least 1 inch wide and 8 inches long. These marks should be placed on trees or fence posts at a height between 3 and 5 feet from the ground, and they should be spaced no more than 100 feet apart. The idea is to create a visible and consistent barrier that clearly communicates “Keep Out.”

When it comes to choosing paint, latex or spray paint works well for trees because it adheres easily and won’t harm the bark. Any durable outdoor paint can be used on fence posts. The key is to make the markings highly visible and weather-resistant, so they remain intact over time. It’s also important to ensure that the property lines you’re marking are legally accurate—this isn’t something you want to do based on rough estimates.

If you’re not planning to mark your own property but just want to be more observant while traveling, the best rule of thumb is to stop and assess whenever you see purple markings. Whether you’re on foot, driving a vehicle, or even flying a drone, purple paint is your cue to respect boundaries and avoid potential conflict. In some states, ignoring these warnings can result in trespassing charges or hefty fines. It’s always better to take a few extra steps to go around marked areas than to end your outing with legal trouble.

So, next time you’re out exploring with your family or friends, remember to keep an eye out for that purple paint. It may not come with flashing lights or bold lettering, but its meaning is just as important. Being informed about purple paint laws isn’t just a quirky fact—it’s a smart move that helps keep your adventures safe, legal, and respectful of others’ land.