Our Colors Don't Run

The exact red, white, and blue colors to be used in the flag are specified with reference to the CAUS Standard Color Reference of America, 10th edition. Specifically, the colors are "White", "Old Glory Red", and "Old Glory Blue".[8] The CIE coordinates for the colors of the 9th edition of the Standard Color Card were formally specified in JOSA in 1946.[9] These colors form the standard for cloth, and there is no perfect way to convert them to RGB for display on screen or CMYK for printing. The "relative" coordinates in the following table were found by scaling the luminous reflectance relative to the flag’s "white"
As with the design, the official colors are only officially required for flags produced for the U.S. federal government, and other colors are often used for mass-market flags, printed reproductions, and other products intended to evoke flag colors. The practice of using more saturated colors than the official cloth is not new. As Taylor, Knoche, and Granville wrote in 1950: "The color of the official wool bunting [of the blue field] is a very dark blue, but printed reproductions of the flag, as well as merchandise supposed to match the flag, present the color as a deep blue much brighter than the official wool."[11]

Sometimes, Pantone Matching System (PMS) approximations to the flag colors are used. One set was given on the website of the U.S. embassy in London as early as 1998; the website of the U.S. embassy in Stockholm claimed in 2001 that those had been suggested by Pantone, and that the U.S. Government Printing Office preferred a different set. A third red was suggested by a California Military Department document in 2002.[12] In 2001, the Texas legislature specified that the colors of the Texas flag should be "(1) the same colors used in the United States flag; and (2) defined as numbers 193 (red) and 281 (dark blue) of the Pantone Matching System."[13]