Candle use in magick

Since the question was asked of magick, and not just of witchcraft, I shall answer from a different perspective. Candles are a source of light- light can be a symbol in some traditions for divinity and for illumination amongst other things.

Colour is another important aspect in some traditions. Some traditions may use correspondences to attune the awareness to a certain principle. This is exactly one of the uses of the Hermetic Qabalistic system. In my opinion colour can be a very important aspect in ritual and meditative practices.

So what can candles be used for in magick? Pretty much any viable ritual/spell.