Yes and yes.
Semaphore or signal flag.
The Swiss flag Swiss flag inspired the Red Cross flag in reverse color
Mailbox?
In the US, when the flag is up it means there is outgoing mail in the mailbox to be picked up by the letter carrier. This alerts the letter carrier to stop at the mailbox even if s/he has no incoming mail to leave for the addressee. When you get ready to mail a letter, leave it in the mailbox and raise the flag. When the letter carrier arrives s/he will take the mail you left in the mailbox, leave any mail s/he might have for you and lower the flag. The flag can also serve as an indication the letter carrier has come and left mail, but it's generally thought inconsiderate to use it for that purpose alone because if the letter carrier has no mail for you it forces him or her to make an unnecessary stop.
the color that end on the flag is red
flag color
Yes, as long as it isn't stolen mail. No, it is illegal, even to place a flyer on the flag. The mailbox is US Government property.
It depends on whose flag it is. But the flag has the number and the base color of the car on it.
Green is the color closest to the flag.
The color of the Union flag was red, white, and blue. It looks similar to the modern American flag.
Yes. It is a Federal offence. But--it is never enforced.
yes put the flag up so he knows its there