Start with 1-3 drops per 500ml of liquid wax and then increase for a stronger colour. Experimentation is key, always keep a record for future reference. You will need to test burn your candle to see if you need to wick up or not, when using alot of colour. NOT SUITABLE FOR SOAP.
Test: Stir colour well, then drip some of your coloured wax onto a piece of wax proof paper, let set and this will be the colour you will end up with.