Colors are an essential part of our lives that signifies things like emotions, people, culture, and in this case, spells.
Burning candles is an effective practice that is believed to connect the physical world to the spiritual world and enhance psychic powers.
Colors for candles are not selected randomly. A lot of spiritual significance is placed upon choosing a candle for a specific purpose.
Candle symbolism in worship is used in different cultures and religions, but in this case, knowing the meaning of the colors of candles adds specificity to the roles of the candles, which makes meditation and spell-casting more precise.
Knowing the meaning of colored candles and applying them in rituals and meditations are crucial to achieving a high spiritual state.

White is often seen as a ‘pure’ color as well as where every other color originates. It symbolizes consciousness.

Gray colored candle is used during the pondering of complex matters because it is a neutral color.

Black-colored candle does not and should not represent evil or harm. Instead, it should be used in rituals or spell-casting to protect from harm.

Red represents a wide range of things like love and danger. It also represents lust, courage, anger, energy, fertility, and physical pleasure.Burning red candles for meditation helps you connect to the physical world, which involves pleasure, desire, success, and joy.

Brown candles are used when you need to cast spells or perform rituals for balance, reconnection, or rediscovery of lost friendships and family ties; and eliminate chaos.

With Orange-colored candles. You need to be bold and it means you require aggressive and instant change, powerful like the fire.
This can be used to achieve success in weddings or businesses as your boldness creates excellent opportunities.

Yellow is a vibrant color, and as such, it is burned when you seek something energetic. It symbolizes the mind, memory, and intelligence.

Gold represents wealth and good fortune. Because of this, those who seek power, success, protection, and fortune/wealth should burn gold candles.

Copper symbolizes fertility. You should burn a copper-colored candle if you seek growth in your career or business.
Burn a copper candle if you want an enhancement or promotion in your line of work, as well as if you meet a roadblock while pursuing your passion.

Silver candles are burned by those seeking to get broader intuition. It plays a massive role in telepathy.
It is believed to have lunar/feminine connections and cosmic energy and, as such, helps to improve reflection during meditation and removes negativity.

Exerts taken from : https://www.colorsexplained.com/candle-colors-meaning/

Color also can just be a personal choice, or used to add accents to your decor, or for any other options that the user feels comfortable with. 

We mix colors with the best efforts towards conformity, but colors may vary slightly from batch to batch due to the chemical balance of the wax and composition of the fragrance batch used. 
We use only all natural products, and these products tend to maintain a lighter color tone than oil based waxes.