Candles have been used in ritual work as well as focal points and concentration aids for centuries. Each different color has a different meaning for both internal and external uses.

Here are a list of uses, from Charles Butler:
 

        OUTER WORKS        INNER WORKS
RED        Energy            Courage
ORANGE        Generosity        Plenty
YELLOW        The Unknown        Centering
GREEN        Prosperity        Healing
BLUE        Love            Emotions
PURPLE        Inspiration        Spirit
PINK        Revelation        Joy
BURGUNDY    Passion            Rekindling
BLACK        Comfort            Authority
WHITE        Vision            Protection