Cool Hair Color Developer Ratio References. Web color & developer ratio q: Web always use a plastic bowl, not metallic, to mix your hair color and developer.

Web get the best hair colour result with the perfect mixing ratio for your hair colour and developer. Depending on the results you want to achieve, mix your developer and. Web usually, the mixing ratio of hair color and 20 volume developer is 1:1, it means the amount of hair color you want to use is equal to the amount of 20 volume.