Wiccans call upon the powers of the Elements in ritual and other Magickal work. Across the board, the four classical Western Elements are included, being Earth, Air, Fire, and Water. Some of the time, a fifth is included, the Element of Spirit, sometimes also called Akasha or the Ether. Each Element has many common associations, although some may differ between individual, Coven, and Tradition.
There are other associations as well, but these are the more basic ones.
In ritual, the Elements are each called in turn to watch over and lend strength to the workings that will be performed (it should be noted that the most common places to begin calling the Elements are North and East, and there are compelling reasons for both). Often physical representations of the Elements are present on the altar or at the edges of the ritual space in the appropriate direction. It is also very important to dismiss or banish the Elements at the end of ritual; imagine the unchecked power of Fire hanging about!
The Elements as a group are sometimes called the Quarters, as the space between each is one quarter of the ritual space, or the Corners or Directions.
There is a bit more to discuss in relation to the Elements, but as that relates more directly to Tools, I am saving it for that section.
1 - This color association is my own, and I came to it thusly; It is said that Spirit is the combination and perfect balance and harmony of all the other Elements. If that is so, then what are all colors mixed together? Well, first we must decide if we’re talking about light, or pigment. If light, then the answer is white. If pigment, black. This is yet another duality, and as discussed before, Wicca is non-dualistic. So, if we combine black and white, the result is grey, or perhaps silver. This makes more sense to me than purple, which is red and blue, and while can be send to be a blend of male and female energies, to me then excludes the other colors in the spectrum.