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.
Larger postcards can be sent, but they are treated the same as letters; the postage will depend on the postcard's size and weight. Postcards can be sent to any other country for $1.15 if the postcard is no larger than 4.25 inches by 6 inches. Larger postcards can be sent, but the postage will be the same as for letters.