Which of the following conditions might require special treatment due to their resistance to color?

Low porosity hair is characterized by a tightly closed cuticle layer, making it difficult for moisture and chemical treatments, including hair color, to penetrate. Because of this resistance, special treatment such as pre-treatments or using specific coloring techniques may be necessary to achieve desired results. Techniques like heat application or using a clarifying shampoo before coloring can help open up the cuticles and allow better absorption of color.

High porosity hair, on the other hand, has an open cuticle layer and can absorb color more readily, while medium porosity hair tends to accept and hold color more evenly. Normal hair also typically has balanced porosity, allowing for effective color application without the need for special measures.