The red wavelengths of light are the longer wavelengths and the violet wavelengths of light are the shorter wavelengths. Between red and violet, there is a continuous range or spectrum of wavelengths.
The USPS also includes that a large postcard is 49 cents to mail. The maximum size for this postcard is 11 1/2 inches long, 6 1/8 inches high and 1/4 inch thick. This is the same rate to mail a First Class 1 ounce letter domestically. The rates for postage increased as of January 2014.
Along with certain other proposed rate increases, including that for certain postage stamp prices, plans to tick up the cost of sending postcards by the U.S.P.S went into effect May 31st, 2015. As of that date, the fee for sending a postcard First-Class went to $0.35 from one cent lower.