Final answer:
The most effective method for removing an old, dark tint is using a color remover or color correction process designed to reverse the oxidation of hair colorants. Permanent hair dye or lightening shampoos are not suitable for completely removing existing hair color. Professional assistance is recommended for safe and effective color removal.
Step-by-step explanation:
To remove an old, dark tint from hair, the correct method would be c) Using a color remover or color correction process. These products are designed specifically to remove permanent hair dye by reversing the oxidation of hair colorants, taking the hair back to its lightened state before new color is applied. Permanent hair coloring requires the oxidation of compounds like 1,4-diaminobenzene derivative to a quinone state, which then reacts with a coupler compound to form the dye. Over time, all pigments wash out of the hair cuticle, although natural color lasts much longer, and artificial color fades faster depending on the dye pigments.
Using a permanent hair dye will not remove the existing tint but will rather add more color on top of it. A hot oil treatment may help condition the hair but is not effective for removing hair dye. Similarly, a lightening shampoo can gradually lighten hair but is primarily meant for slight changes and not for removing a dark tint completely.
For a safe and effective color removal, it is generally recommended to seek professional help, as the process involves strong chemicals and should match the specific type of dye and hair condition.