Acrylic colour may appear slightly darker after drying. What is this effect called?

Correct answer: Colour shift or drying shift

The governing idea is that a paint colour can look different when its wet film becomes dry. In acrylics, the change may appear as a slightly darker or less glossy colour and is commonly described as a drying shift or colour shift. Therefore option B is correct. Colour separation, light diffraction, and oil absorption describe different phenomena and do not explain this normal acrylic change.