Why do colors have different meanings?

Colors (Colours) are adopted by different people and organizations just as you have a preference for one color over another. After a period of time, these colors began to be associated with that group of people or a character of that person. Thus, purple and deep blue were worn by kings and emperors and became associated with royalty. Thus the term "royal blue". I'm familiar with military history and many countries adopted certain colors for their army. The British became known as the "red coats". A medium blue became known as "Prussian blue". In Germany and other countries, a dark green was common wear for those who worked with the forrests. Thus rangers and hunters were identified with this green, which has been passed on through other countries and even down to the US Green Beret special forces. It is all based upon association.