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.
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. The exact rate will depend on the destination country, as well as the size and weight of the postcard.