For actual stamps with this theme, head over there.
Independence day happened recently, and I sent this piece to The Artist in Seine.
I found an image of stamps I used to send a package a while ago, featuring red and blue stamps.
Two stamps from the lead up to the New York World Stamp show, issued in 2015. The $2 stamp celebrating the postal error of the upside down Flying Jenny stamp printed using the intaglio technique, and a 46c patriotic star, both issued in 2013.
USPS controversially printed 100 sheets (6 stamps per sheet, sold inside an opaque envelope) of inverted Flying Jennys out of the several hundred thousand print run that were randomly distributed to post offices and the stamp fulfillment service center, thus fabricating a rarity. Despite the controversy, the rarer stamps are currently worth tens of thousands of dollars. The value of $2 was also controversial - no domestic rates are that high, so the stamp does not see much use in regular mail. The original error stamps were valued at 24c, and are currently worth in the hundreds of thousands of dollars.