Today is the fourth Sunday of Advent when the third and last purple candle is lit. It is often called the "Angel's Candle," because they announced the King's birth. This candle represents peace.
On Christmas Eve, the center white candle will be lit. It is the "Christ Candle" representing Jesus Christ who came into the world to bring us salvation. White symbolizes purity, and Jesus is the sinless, spotless, pure Savior. Those who accept Jesus as their Savior are cleansed of their sins and made whiter than snow.
"The virgin will be with child and will give birth to a son, and they will call him Immanuel" - which means, "God with us." Matthew 1:23