Wiccans believe that certain colors represent certian things or emotions. These colors, when used in magick, can greatly help to focus your concentration. If you want to do a money spell, then use a green candle. If you want a love spell, then use red or pink. For more on this, read my Spell page.
Yellow: represents itelligence, communication, divination, enlightentment. This is the color of the sun and therefore, can be used to represent the God during your rites. It also represents air.
Red: represents passion, sex, physical energy. It stands for the element of Fire. It is associated with blood, life, and death.
Orange: represents success and attration.
Blue: represents healing, peace, and happiness. Blue is the color of Water. But watch out! Dark blue represents depression.
Pink: represents friendship, love. This stands for more calmer emotions versus red.
Green: represents money, prosperity, fertilty, growth, nature. Green is the color of Earth.
Purple: represents power, spirituality.
White: represents peace, purity, protection. It symbolizes the moon. You can use this candle to represent the Goddes in your rituals. Since white is the base of all colors, it can be used instead of other colors that you may not have available.
Brown: represents animals. Earthy stuff.
Black: represents wisdom, banishing or absorbing negative energy.