This is a great question, which people rarely think about.
When it comes to the American flag there are many symbols that are used. As you know the color of the American flag is red, white, and blue. From a historical prospective, the continental congress did not accord the colors of the flag with any special meaning. If they did, it was not communicated.
The best that we can do is go by Charles Thompson's interpretation. He was the secretary of the Continental Congress and in 1989 published a book entitled, Our Flag. In this book he stated the following. The while signifies purity and innocence. The red signifies hardiness and valor. The blue signifies vigilance, perseverance, and justice.
trust me it meanse alot. I am ethiopian we have a flag which containce three colours green, yelow and red, and their is a blue based star. This flag was diferent inthose previous governerse of ethiopia, simply it doesent hav the star. the gren color shows the green forest and plantation of the country, yelow represent the peace of the country (it is real on the past emperial redgems because they concour diferent nationce and nationalities) and red shows that the contry have been deffend by her patriots from envadors. for the star sown in the middle of the flag it has a great mining, it is shows the multi nations that bring their difference for a buty and stand together for a better futuer and better life.so i kan asure you many country flags colour shows their history and their feutuer.