Happy New Year!
This year (2011) the standard queen marking colour is WHITE.
A different colour is used for marking honeybee queens each year based on the year in which the queen is reared. Five different colours are used as standard on a repeating cycle and as queens do not live for more than five years, there is no confusion.
Marking queens in this way serves two purposes, first marked queens are easier to find when inspecting the colony and second, the colour code enables the beekeeper to keep track of the age of the queen in the colony.
The colour code is based on the last digit of the year:
Year ending: 1,6 White
A simple way to remember it is Will You Rear Good Bees (White, Yellow, Red, Green, Blue)