Which of the following characteristics does not accurately describe semi-permanent colours?

Semi-permanent colours are designed to provide a deposit of colour onto the hair without altering the natural pigment deeply, which is a key characteristic. They typically last longer than temporary colours while not requiring a significant chemical change in the hair structure. One of the defining traits of semi-permanent colours is that they do not leave a strong line of demarcation when they fade; instead, as the colour gradually washes out, it typically blends more evenly with the natural hair colour. This blending effect is advantageous, as it reduces the harsh contrast that can occur with more permanent hair colour methods. While semi-permanent products can be easily shampooed out over time, their ability to deposit colour without a chemical change is a critical feature that aligns with the characteristics of this type of colour treatment.