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RGB - the additive way of building colours
RGB stands for Red, Green and Blue and the system used on display screens to generate
colours.
Screen colours are constructed from red, green and blue fluorescent phosphors (or other light emitting component, depending upon screen type) on the screen sighted at each pixel position. Each of the three colour elements making up a single pixel may be set to one of 256 values (ranging from 0 to 255). A value of 0 means that the relevant colour is not visible at that pixel and a value of 255 would cause the colour to be shown with the maximum brightness.
All of the colours that you see on your screen are constructed from the relevant constituents of red, green and blue. As there are 256 possible values for each element the total number of colours that can be displayed on a (true
colour) screen is therefore 16,777,216
There are 216 RGB colour values that are known as the Browser Safe set. If you are building HTML pages (or maps to display on the Internet) and you want your colour selection displayed as accurately as possible then you should select them from this group. To view the Browser Safe colour set click on one of the links below.
The 216 Browser Safe colours with their decimal RGB codes.
The 216 Browser safe colours with their hex codes – ready to use in your HTML code.
CYMK - colour subtraction
CYMK (or CMYK) stands for Cyan, Yellow, Magenta and blacK and is the system used in many print processes to generate
colours. Inkjet printers are a very good example – they generate the whole range of natural colours (often to near photographic quality) from just three or four coloured inks plus the white of the paper they are printed on.
The use of coloured inks to achieve an image is known as a subtractive process. An area of yellow is the result of a pigment that absorbs (or subtracts) all of the other two colours to achieve the result.
The conversion of screen RGB colours to print colours is not perfect. There are only around 1,000,000 colours supported by the CYM system. The inks used by the process have some significant imperfections and this makes it difficult to achieve some
colours. If the three primary colours are mixed together then instead of
black we would normaly see only a dirty brown - this is why black ink is added as a fourth component. Bold and bright
(especially very light) colours can’t be printed and there are significant gaps in the shades of
green and blue achievable.
More Information on Colours
For all you wanted to know on the technical issues of colour and colour reproduction try
http://www.poynton.com/ColorFAQ.html
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