All About Colour

Computer screens make colour by mixing three different colours of light :

Red, Green and Blue.

This system is called RGB.

Move the colour circles of light in the window below to see how the different colours mix.
How do you make purple light?
How do you make yellow light?
How do you make white light?

The circles above show only a few colours, but computer files can remember millions of different colours.  That is because for red, green and blue, the computer can remember 256 different shades ranging from black to the pure colour - as shown below.

Colour is saved in files by storing the amount of each colour used.  256 different amounts can be remembered for each colour and so each colour is given a value from 0 to 255.  As there can be 256 shades of red, green and blue, this makes:

256 x 256 x 256 = ?

Open the calculator (Start>Programs>Accessories>Calculator) and work out how many possible colours can be remembered by the computer.
(This is called 24 bit colour as each pixel uses 24 bits of memory.)

This square has values Red-125, Green-0, Blue-0  
This square has values Red-125, Green-125, Blue-0  
This square has values Red-125, Green-125, Blue-125  
If all the values of R,G and B are similar the colour made is grey. 
In this next exercise try to match the colour of the box on the left to the box on the right by adjusting the values for R, G and B.



CLICK HERE to try a much more difficult version of the above game.
Some programs may ask you to select which colour you want by selecting values for hue, saturation, and brightness.

Hue is what colour is, e.g. blue, red, pink, orange, brown etc.

Saturation is how pure the colour.  High saturation gives a pure colour such as bright red and low saturation gives a greyer tone.

Brightness (or Luminosity) is how light the colour is.  Low brightness gives a dark shade and high brightness gives a light shade.

Open Microsoft Paint (Start>Programs>Accessories>Paint) and select edit colours from the Color menu.
Compare values of RGB and HSV for different colours.