For serious candle makers... EazyColours Super-Strength Wax Powder.
This is the strongest product you can get for colouring candles and just 1g can colour up tp 12kg of wax, depending on wax type and colour depth required.
Colours can be mixed to create other colours.
The easiest way to handle this product is to make wax chips
CI 61554
Picture shows performance in soy wax.