Apparently orange is purple too.

"In other states, such as Idaho, Montana and Arizona, orange is the color of choice for “No Trespassing” paint.

Can you get shot if you trespass?
Despite what many people may tell you, it’s not legal for landowners to shoot you if you happen to wander past one of these purple markers, however they do have the right to remove you with force if you’re caught trespassing."