An application of which colours would help to reduce the client's hair of orange tones?

To reduce orange tones in hair, the application of blue-based colours is effective. This is based on the principles of colour theory, where complementary colours are used to neutralize undesired hues.

Orange is directly opposite blue on the colour wheel, which means that blue can effectively cancel out the bright, unwanted orange tones in the hair. When blue pigments are applied, they counteract the warmth of the orange, resulting in a more balanced and neutral tone. This technique is often utilized in colour correction processes to achieve a desired shade, especially for clients who have previously dyed their hair and are experiencing brassiness.

In contrast, while other colours, such as red-based tones, might offer some level of correction, they would not address the orange tones as directly as blue does. Yellow-based colours can potentially enhance the warmth rather than neutralize it, leading to an undesired effect. Green-based colours are typically used to combat red tones and would not be suitable for orange. Hence, the choice of blue-based colours is the most effective method for reducing orange tones in hair.