What is hair colour?
Without going in to chemistry side of it colour is an artificial pigmentation that break into the hair shaft to change the natural or already coloured hair. There are 3 types of hair colour, permanent, semi permanent or temporary.
Permanent does not mean that the artificial color will remain permanently. The natural hair is permanently chemically altered but pigmentations will fade and change over time. If grey coverage is required permanent colouring is the best option.
Semi Permanent does not break into the hair shaft but rather sits on the outer cuticle. Semi permanent wash out over time, about 4-6weeks. You can also only colour at same level darkness or go darker with semis.
Temporary Colours are those vivid fashion shades of amazing blues, pinks and purples. These colours are just that temporary and will only as vivid for a few weeks.