Sea of red, white, and blue; photo by Pieter TER KUILE on Flickr (noncommercial use permitted with attribution / share alike).
Official Colors of the USA
The official national colors of the United States can be seen on the American flag; red, white, and blue. All State Colors
Although the colors did not have a specified meaning at the time the American flag was adopted, they were defined for the Great Seal of the United States in 1782: Red is a symbol of valor and bravery, white symbolizes purity and innocence, and blue signifies vigilance, perseverance, and justice.
From United States Department of State's website; Charles Thomson’s “Remarks and Explanation,” detailing the symbolism of design elements on the Great Seal, adopted by the Continental Congress, June 20, 1782 (Charles Thomson was the Secretary of Congress):
"The colours of the pales are those used in the flag of the United States of America; White signifies purity and innocence, Red, hardiness & valour, and Blue, the colour of the Chief signifies vigilance, perseverance & justice. The Olive branch and arrows denote the power of peace & war which is exclusively vested in Congress. The Constellation denotes a new State taking its place and rank among other sovereign powers. The Escutcheon is born on the breast of an American Eagle without any other supporters [figures represented as holding up the shield] to denote that the United States of America ought to rely on their own Virtue."