In most states, you'll often come across a "No Trespassing" sign on remote and private properties; in Texas, you'll just see purple paint. 

It all began in Arkansas back in 1989, according to MyEastTex. Property owners used purple paint as a subtle way to remind visitors, most notably hunters, that they're nearing a private area. In 1997, Texas put the law into effect. Jonathan Kennedy told the news outlet that this would put an end to property owners having to replace their signs, which were often used for "target practice."
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Ashley Pellerin, a Prairie View A&M Extension agent, believes the color purple was used because those who are colorblind can still see it. The law says the vertical purple markings must be clearly visible, and should be 8 inches long by 1 inch wide. 

The Purple Paint Law is also in effect in the state of Illinois, where lawmakers hoped that the markings would deter hunters. "Most hunters are very respectful," Illinois Forestry Association Secretary Dave Gillespie told the Chicago Tribune, "but there are always bad guys who aren't and ruin it for the rest of us."

Former state forester Ed Waddell had a different explanation as to why property owners used the color purple. In fact, Waddell was appointed by lawmakers to choose a color that was without a significant meaning to the forest industry. He told the Tribune that he was left with just a handful of colors to choose from, but purple seemed to stick out the most amongst the trees.

If you ever find yourself in rural Texas or lost in the Illinois countryside, just remember that purple paint doesn't indicate a warm welcome.