School colors
Common primary colors include orange, purple, blue, red, and green.  These colors are either paired with a color representing a metal (often black, brown, gray (or silver), white, or gold), or occasionally each other, such as orange/blue, red/green, or blue/yellow.  Pairing two metals, such as black/white, silver or gold, and especially black/gold, is also a common practice.   Finally, some American schools, in a display of patriotism, adopt the national colors of red/white/blue.