Why do other producers’ colours alter over time, turning orangish or bluish/purplish?

Colour alterations depend on the raw materials used for their production, stabilization processes, and a series of other factors, such as medications, exposure to sunlight, ph alterations due to the use of aggressive detergents, inadequate after-care treatments, wrong colour for skin undertone, and use of incorrect products during the procedures. There is a full plethora of causes for colour alteration which should be covered during the training.
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