I'm bending the Sunday Stamps rules today, where the theme is 'the color red'. Actually, I pretty much threw the rules out of the window and let a passing band of animals trample them. Just kidding, you can skip the mail art part and find my red(dish) stamps below.
For actual stamps with this theme, head over there.
Independence day happened recently, and I sent this piece to The Artist in Seine.
Update:
I found an image of stamps I used to send a package a while ago, featuring red and blue stamps.
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.