The colorful spot you sometimes see on a queen’s thorax is actually a code. The color denotes the year of the queen’s birth. So with a just a quick look, you can tell how old she is. The International Color Chart works like this:
Years ending in 0 or 5 are blue.
Years ending in 1 or 6 are white.
Years ending in 2 or 7 are yellow.
Years ending in 3 or 8 are red.
Years ending in 4 or 9 are green.
Since queens normally live just a year or two, the color chart repeats every five years. Besides dating her, the bright paint spots makes it much, much easier to find her majesty among the tens of thousands of workers and drones.