Spectrum Merino uses dye-resist treatment to make selected fibres or yarns take up less colour than untreated wool. Woolmark describes combining the two before later yarn, fabric or garment dyeing. Their different responses create two-tone effects, while suitable coloured blends can form multicoloured melanges.

Spectrum Merino Creates Marl Effects Through Different Dye Uptake

This matters when identifying a marl-looking textile. The visible shade mixture need not mean every final colour was fixed before spinning. Differential dye uptake provides another route to the appearance, allowing later colour decisions while the underlying wool construction remains in place.