Double action candles are candles with two colors of wax sandwiched on top of each other - half black and half another color, usually white, red, or green. You use these candles to move out the bad - banish, cleanse, reverse, remove - and invite in the good - bless, attract, improve, honor.
Use double action candles several times a year during certain lifetime events involving change, and whenever you need to move out a bad spell of luck or sadness or an unfortunate event.
Different color choices stand for different conditions. Red and Black candles are used for love and relationship matters (marriage problems, divorce clearing, moving past a broken heart, removing damaging personal habits before starting a new relationship, etc.); Green and Black candles are for money and employment-related workings (changing irresponsible financial patterns, money worries, picking yourself back up after bankruptcy, living without alimony, monetary lawsuits, job concerns, etc.); and White and Black DAs are for everything else (spiritual work, healing, bad habits, miscellanea, etc.)
Yellow. Courage, success, and confidence all come to mind with the color yellow, but what you'll really want to hone in on with a yellow candle is joy.