CHICAGO (CBS) — Mailboxes are supposed to be blue, but some Chicago neighborhoods are seeing them in green or black – confusing customers.

WBBM Newsradio’s Steve Miller explains.

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The mailboxes start out blue. Then, probably after some graffiti is scrawled on them, someone is painting over them in green or black paint.

U.S. Postal Service Spokeswoman Robin Anderson says it must be someone with good – but misguided – intentions.

“We need our boxes to be blue,” she says. “They’re causing us extra work, and we have to cover what they’re doing, where we could just go out and clean up the graffiti. And it’s causing confusion.”

It’s confusing because customers sometimes think it’s not a real mailbox.

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Who’s to blame?

Anderson says the post office sent a directive to the City of Chicago a few months ago, asking the Department of Streets and Sanitation, which tackles graffiti, to leave the mailboxes alone.

But a department spokeswoman says city workers aren’t the culprits.

“It’s not our policy to paint these mailboxes.  But we have issued a reminder to our crews to refrain from painting any mailboxes,” Anne Sheahan says.

Regardless of who is doing it, the post office says the mailboxes don’t look legitimate.

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“It causes confusion with the customers. They don’t know what’s going on. Is it a real box? Our color is blue,” Anderson says.