To enhance the longevity of hair color, clients should avoid which of the following?

To enhance the longevity of hair color, clients should avoid swimming in chlorinated water. Chlorine is a chemical commonly found in swimming pools and is known to strip hair of its natural oils as well as any artificial color. This can lead to fading, discoloration, and increased dryness of the hair, which diminishes the overall vibrancy and longevity of the color treatment.

On the other hand, using a silk pillowcase can actually benefit colored hair by reducing friction, which helps prevent damage and breakage. Applying leave-in conditioner is also beneficial as it provides moisture, protection, and helps maintain the color's vibrancy. Using a wide-tooth comb is recommended for detangling hair gently, especially when it is wet or has been color-treated, further supporting hair health and color retention.