Mysterious colored dots on our mailboxes just showed up the last day or two. What are these about?

Mysterious colored dots on our mailboxes just showed up the last day or two. What are these about?:

What are these about? Somebody has put mysterious dots on the mailboxes in my subdivision in the last day or two. These are thick reflective dots about an inch in diameter. The one dot on my mailbox is yellow. My next door neighbor has a red dot. My other next door neighbor has 3 green dots. Neighbor down the street has 2 greens and a blue on theirs. They are on both sides of the mailbox, stuck right onto the mailbox itself, not the post. I drove a little throughout the town and many mailboxes have no dots on their mailbox, while their next door neighbor has the dot(s)....
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