How long does the colour last and how does it fade?

Semi-permanent direct dyes sit on and around the cuticle rather than inside the cortex, so every wash removes some pigment. On highly porous, freshly bleached hair the initial saturation is strongest but it also rinses out faster — often noticeable fading after 3–5 washes. On less porous or only lightly lightened hair the colour may remain visible for 10–12 washes. Sulphate shampoos, hot water, and frequent washing accelerate fade; cool water, sulphate-free cleansers, and washing less often extend it. As the blue fades on a yellow-blonde base it can pass through teal or greenish stages before returning to the underlying blonde. There is no sharp root line because the product does not alter new growth.