R=Red light
G=Green light
B=Blue light

Every single colour (including white or black) is made up of a numerical value of these colours. Each tiny area ranges in intensity of light from the three colours (imagine 3 lightbulbs brightness with a dimmer knob), from 0 (off) ...to 255 (brightest).

So to get started, we look at the three basic numerical values of RGB in their pure (brightest) form:

Red.
Value is: R- 255; G- 0; B- 0

Green.
Value is: R- 0; G- 255; B- 0

Blue.
Value is: R- 0; G- 0; B- 255

Getting the idea now?

Below we have a more detailed example:

A picture of a pretty butterfly, (I have outlined an area in red, which I have zoomed right into below):

Now, the zoomed area, made up of "pixels" (blocks of colour):
(I outlined one of the blocks in red to give you the colour breakdown of that block as an example below)

The red outlined block shows the following RGB values:

R (red) = 0;  G (green) = 230;  B(blue) = 255

(As a matter of interest, the darker blue block on the bottom right is: R = 1;  G = 168;  B = 252)

White, is R-255; G-255, B-255 (the full intensity of all three colours, if you shine a red, green and blue torch onto the same spot on a wall, at the same time, it would be white. (Remember we did those experiments in Science class at school? Well this is it, in action.)

Black is simply R-0; G-0; B-0 (The lights are off, in other words).

Now we move on to CMYK.

CMYK refers to a PRINTING process. When you have full colour brochures, photos, posters or adverts printed, it is made up of four colours.

These are:

C- Cyan
M- Magenta
Y- Yellow
K- Black (it is believed that the use of the abbreviation "K" instead of "B", originates from the German word "Kohl" for black)

The inks are measured in percentages from 0 - 100%.

So let's break down the basic numerical values of CMYK in their pure (brightest) form:

Cyan.
Value: C-100; M- 0; Y-0; K-0

Magenta.
Value: C-0; M-100; Y-0; K-0

Yellow.
Value: C-0; M-0; Y-100; K-0

Kohl/Black.
Value: C-0; M-0; Y-0; K-100

Using various printing presses, state of the art, or older systems, these four colours mixed make up a full colour print.

Let's look at a CMYK breakdown in a more detailed example:

A picture of a pretty Discus tropical fish, (I have outlined an area in black, which I have zoomed right into below):

Now, the zoomed area, also made up of "pixels" (blocks of colour):
(I outlined one of the blocks in black to give you the CMYK colour breakdown of that block as an example below)

The highlited block shows the following CMYK values:

C (cyan) = 1%;  M (magenta) = 77%;  Y(yellow) = 100%; K(black)=0%

(As a matter of interest, the warm yellow block on the bottom right is: C = 11;  M = 27;  Y = 100; K = 0)

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Related: Printing Registration which we will cover in a future article.