Candles are popular and used tool in spellcrafting. Reason for this is most likely easiness of their use, which all you need is selection of the candle. You can use candle just as them in magic, but also in spell binding, enchancing and only calling in certain energy or matter.
Most wiccan consider that the candle color effects the duration or effection of the spell, others consider them as a symbolic effect. Whatever you consider, it is good to remember that some colors vibrate more than others: White repels energy and protectes when black absorbs it.
Candles can be used as it, but many consider inscribing or engraving signs, symbols, runes or words to them to enchance or target a spell.
List below has most common colors used in candles: