Young Girl With Light Colored Hair

The chemical formulae of alternative color dyes typically contain only tint, and have no developer. This means that they will only create the bright color of the packet if they are applied to light blond hair. People with darker hair (medium brown to black) will need to use a bleaching kit prior to tint application. Some people with fair hair may benefit from prior bleaching as well. Gold, yellow and orange undertones in hair that hasn't been lightened enough can adversely affect results, especially with pinks, blues, and greens. Although alternative colors are semi-permanent in the cases of some colors, such as blue and purple, it could take several months to fully wash the colour from bleached or prelightened hair.
Adverse effects of hair coloring
Hair coloring involves the use of chemicals capable of removing, replacing and/or covering up pigments naturally found inside the hair shaft. Use of these chemicals can result in a range of adverse effects, including temporary skin irritation and allergy, hair breakage, skin discoloration and unexpected hair color results.