Colour- The Basics:
Light is composed from three “primary” colours, green red and blue. Mixing any two of these colours results in yellow, cyan and magenta, and mixing all three results in white. When white light is projected onto an object certain frequencies of light will be absorbed and the light reflected is the remaining colours.
Right: Mixing colours of light
Left: How we see light
As your hair colour is dependent upon the light reflecting from within the hair shaft viewing hair, both natural or dyed, under different kinds of light e.g. UV or fluorescent can dramatically change the hair colour as the projected light is a different composition to natural sunlight.
Just as mixing light can result in new colours it can also cancel out certain colours. Colours that are opposite to each other on the colour wheel will cancel each other out. This can be useful in some cases, often people with bleached hair find that after swimming in a chlorinated pool caused their chemically treated hair acquires a green tinge. This can be easily reversed by “washing” the hair with tomato ketchup as the red dyes cancel out the green. However this cancelling effect also make certain hair dyes impossible to make such as permanent pink due to the natural green undertones in the hair.
Using the effects of mixing and cancelling light one can be creative in designing new shades for your hair, especially with the use of semi permanent or temporary hair dyes.
Hair dyes can produce a wide range of highly colourful results (examples in the Photo gallery). Permanent hair dyes tend to give more natural tones, browns blondes reds blacks and purples. These are limited by the chemical reactions that take place within the hair. Semi permanent and temporary hair dyes are much less restricted, producing any colour from bright green to bright pink.
However little is known by the public about the specific chemicals within dyes that produce the different colours, due to the secrecy of the manufacturing companies.