Answer: White means purity and innocence, Red means hardiness and valor and Blue means vigilance, perseverance, and justice.
According to USFlag.org, the Founding Fathers came to a consensus that the colors red, white, and blue had no specific meaning for the American Flag. Instead, the significance of each color referenced above was intended for the Great Seal of the United States. Eventually, however, the meaning of the colors of the Great Seal morphed into the same meaning for the colors of the American Flag. Below is the Great Seal of the United States. Do those Latin words look familiar?
Pictured: The seal being pressed down on a wafer with the American Flag in the background. Public Domain.