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factfile2.8 RGB Colours

 

Web colours are represented by the combination of Red, Green, and Blue colour values. The value for each colour ranges from 0 up to 255. Pure white contains all three colours at their maximum values – so Red is 255, Green is 255 and Blue is 255. Black contains none of the colours, so their values are all set to 0.

The HTML language for coding web pages uses hexadecimal (Base-16) to denote the colour combinations. Hexadecimal also uses the letters A-F and counts in 16’s and units as oppose to 10’s and units in decimal (base 10). So 16 in decimal is 10 in hexadecimal. 255 in decimal is FF in hexadecimal. The HTML code is a six digit code, with two digits for red, another two for blue and two more for green. 

 

 

For example the purple colour above may be coded like this:

hex colours

All colour codes start with a # sign. So this colour would be referred to as #663399. Here are some colours with their RGB values, and their hex equivalent.

hex colours

You can read more about hexadecimal here: http://en.wikipedia.org/wiki/Hexadecimal

The combination of Red, Green and Blue values from 0 to 255 gives a total of more than 16 million different colour combinations (256 x 256 x 256) (which is actually 16,777,216), although in practice there are fewer individual colours since it is hard for the eye to tell the difference between some of them.

A few years ago, when most computers only supported 256 different colours, a list of 216 Web Safe Colours was suggested as a web standard. The reason for this was that the Microsoft and Mac operating systems used 40 different "reserved" fixed system colours (about 20 each). You can see this full palette at http://www.lynda.com/resources/hexpalette/hue.html

It’s less of a concern today, since most computers have the ability to display thousands of different colours, (modern monitors are capable of displaying at least 16384 different colours) but designers try to stick to these “web safe” colours. This is especially important with the increase of people using tablets and smartphones to access the internet. Remember, not everyone is using a high speed home computer to browse the web, although the graphics capability of these devices is getting better and better and won't be such a concern in the future.

For more information on web colours, visit www.w3schools.com/html/html_colors.asp and also http://en.wikipedia.org/wiki/Web_palette

pushpin A guide to RGB colours

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