Regular shampoo cleans. Colour shampoo either adds pigment back (a colour-depositing shampoo) or uses gentler surfactants so it doesn't strip dye out (a colour-protecting shampoo that Australia's salons rely on for aftercare). Most everyday retail shampoos use stronger detergents that fade dyed hair quickly, especially in the first two to three weeks after a service when the cuticle is still settling.

Yes, and that's exactly what they're built for. Two or three washes with a depositing shampoo will visibly refresh a fading tone and push the gap to your next appointment out by several weeks. It's why most Australian salons send clients home with one as part of aftercare.

Strong pigments, bright purples, blues, and reds can leave a faint mark on white tiles or porous towels if left to dry on the surface. Rinse the shower walls after use and stick to dark towels for the first few washes. Pigment lifts off skin easily with normal soap and warm water.

Often, but not always. Most colour-protect shampoos sold in Australia are sulphate-free or sulphate-light because sulphates accelerate fading. Always check the ingredient list, though. "For coloured hair" on the front of a bottle doesn't guarantee a sulphate-free formula on the back.

Yes, but only to tone it, not to fully cover it. Purple shampoo removes yellow or brassy tones to keep grey or white hair looking bright and cool. Blue shampoo helps if the grey hair has turned orange or rusty. These shampoos will not hide dark grey roots or fully cover white hair like a permanent dye would. For full coverage, you need a stronger product like a semi-permanent or permanent hair dye.

It's rarely permanent, but it can be stubborn. Very damaged or porous hair can hold onto deposited pigment for weeks or months after you stop, while healthy hair will shed it in 4 to 6 washes. A clarifying wash will speed the process up, but use it sparingly on coloured hair because it strips natural and artificial pigment in the same go.