That is a wonderful question, Michelle. Spells8 provides a whole series on candle magic. Here is the yellow candle, specifically.
I borrowed this from the series at some point from Spells8 and use it often. I hope this helps.
Edit: Marissa created the informative, BOS worthy Pentacle Color Magic 
(Hint, Hint, Francisco. LOL) The colors are close to what is used in candle magic. 