Out of all the electromagnetic waves in the Universe, from a billionth of a millimetre short to about 10 km long a tiny spectrum in the middle is visible light, those that measure between 0.00038 and 0.00075 millimetres. When we see the whole colour range together it appears as white, when some of the wavelengths are absorbed by an object, we see the wavelengths that are reflected and perceive them as colour. The colours that we are able to perceive are the colours of our rainbow – Red, Green, Blue Yellow, Indigo and Violet. The purest colours appear in nature in the form of pigments like ochre and indigo, in design we rely on digital colour and printed colour to produce the best representation for us.

RGB Colour

Our standard Digital colour space of Red, Green and Blue (RGB) is known as Additive colour. Digital colour made up of multiple wavelengths of light coming towards us on from our screens. These wavelengths add together to produce colour, the more light is added the whiter it gets. The colour is represented with binary digits 0 and 1, in an 8-bit format which means any combinations of 00000000 (black) to 11111111 (white) with 254 intermediate shades of grey in between. Still with me, apply this to three colours in stead of two – Red, Green and Blue and you get 256 shades of each colour. Mix these three colours or channels together (256 x 256 x 256) and that’s 16.7 million possible colours to choose from.

CMYK Colour

The print colour space of Cyan, Magenta, Yellow and Black (CMYK)  is know as Subtractive Colour. Unlike digital colour, but similar to nature, the colour of print is defined by the wavelengths that aren’t reflected from the visible spectrum of colour. The more colour your add the closer the colour moves towards black.

There are some colours that we can produce in RGB that are not possible to produce in CMYK and vice versa. When we convert an RGB colour image to CMYK image you may notice the color shift. Some colours are very difficult to translate, for example a lovely bright orange on screen can become a bit ‘muddy’ in print, the best way to to get the right result is to either refer to a CMYK colour chart or pick a Pantone colour which is absolute.

Colour is a massive topic but it is interesting to think that what we see it not necessarily what other people see, as individuals can perceive colour slightly differently. An aspect of design for usability is the awareness of colour-blindness or varying colour perception and providing options that will provide better contrast and more clarity of users.