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.
The current postage needed for an international postcard stamp is $1.15 for a standard shaped and size one, in fact it's the same price for a letter of 1oz or less. The USPS lowered the rate from $1.20 back to $1.15 in middle of 2016.