Colour is very complicated – people write PhDs on the subject!
Colour – Pantone Matching System
Pantone colours were introduced when printing was mainly offset litho. The process involved making a plate for each colour that was being printed. Some presses were one-colour, some two-colour and others four-colour.
A plate was made for each ‘colour’ that you were printing. You might have had red and black for example. The printer would then use his black ink and his red ink (whatever he had). Clearly, this meant that colours were not matched from printer to printer.
Pantone Matching System PMS emerged as a standard – it’s exactly like the Dulux mixing in a Homebase. You look at the swatches in Homebase and choose a ‘Tuscan Orange’ – the machine then starts with the blank paint (matt, silk or gloss) and adds proportions of pigments, shakes it up and you have your tin of paint – in just the same way, Pantone produced swatch books, you chose you colour and the printer had the recipe to make up that colour.
Getting consistent ink colour is only one step. The human eye perceives printed colour based on reflected light – if you put the same ink on matt paper, silk paper or gloss paper, the eye will perceive the colours as being different.
Ink is slightly transparent. When you put the ink onto matt (uncoated) paper, the ink is absorbed slightly by the paper. Light is reflected is off the surface of the ink but any light passing through the ink is not reflected from the matt surface, so the colour looks slightly ‘muddy’. When the ink is printed onto a coated surface like silk or gloss, the ink sits on the surface. Light is reflected off the surface of the ink and also, light passing through the ink is reflected from the coated surface, so the colour looks brighter – the glossier the surface, the brighter the colour looks.
Pantone colours became more sophisticated with different ‘recipes’ for the same colour depending on whether the colour was printed on coated or uncoated paper.
There are many other factors such as the surrounding colours, the light (artificial or daylight), the colour of the paper, how large the block of colour is etc, that can affect the perception of colour -even if the same ink colour has been used.
As recently as the early ‘90s, printing in one or two colours was the norm because each plate needed in the offset litho process cost circa £75 to make so if you were printing letterhead, for example, you were paying £75 per colour before you had made a mark on the page – this meant that full-colour (CMYK) short-run printing was not economical.
In the ‘90s digital printing began to come into being alongside the web. Digital printing cut out the need to make plates so printing of short runs became economical. Also, it meant that you could have lots of colours (16.7 million) that can be produced via CMYK.
With CMYK printing, dots are group together in groups of 4 of cyan, yellow, magenta and black. The relative sizes of the dots are defined by the ‘CMYK split’. The groups of dots fool the eye into perceiving the relevant colour. If you look at a CMYK print under a magnifying glass, you will see the dot pattern. The smaller the dot pattern (print resolution) the crisper the image and the colour representation. This, and the web, meant designers started to use many more colours in logos, tint’s blends and shades and pretty much everything is now printed digitally in CMYK.
However, 16.7 million colours may sound a lot but, some colours do not necessarily replicate well in CMYK. Every Pantone Colour has its CMYK equivalent but, interestingly, the CMYK split for a coated colour is different to the CMYK split for an uncoated colour – the CMYK splits are always called ‘approximations’.
Because of this ‘approximation’, some companies that are very protective about their colour(s) might use a process called 5 or 6 colour printing. In this process (it cannot be achieved digitally) for example printing a brochure, the standard CMYK file is produced for all of the graphs, photos, text, charts etc is produced and the logo colour is specified as a spot colour which is added using a separate plate and a specially prepared ink – this is super expensive and is very rarely done.
RGB is the specification used for screens, monitors, phones etc. When you are looking at a colour on-screen you are seeing transmitted light unlike the reflected light of print. Like CMYK, groups of dots, in this case, red green and blue make up the picture and fool the eye into perceiving a colour. Once again, you are working with an approximation of the colour.
This is normally not an issue as people don’t put printed material next to a screen to compare colours.
Using RGB can become a problem when you are printing on an ‘office’ printer. Office printers tend to be CMYK printers – they’ve got four cartridges; cyan, magenta, yellow and black. Most desktop applications, Microsoft Office particularly, work in RGB for view on a screen. When you send a file to print on your office printer, the printer or the print driver have to convert the RGB info into CMYK for printing – there is not any common standard for this.
Colour – what’s the way forward?
Let’s say your designers have created a great logo for you that you like and it’s has a red and a silver. You could think about using spot colour for consistency but there are a few issues that could make this impractical.
- Cost – you would have to go to 6 colour-litho for everything (if you have two spot colours in your logo) which would be significantly more expensive than CMYK printing
- The colours specified in your ‘logo design’ might be for coated paper Pantone XXX C you would need Pantone XXX U for uncoated papers and other variations for other substrates.
- It would be impossible to match the colours on screen – you could try with If you look at PMS recommended splits https://www.pantone.com/color-finder
If you are really concerned about colour consistency, you would get more consistent results if you had everything printed in CMYK on the same substrate, silk, matt or gloss paper – forget about your office printer trying to match colours or reproducing your logo specifically – use printed letterhead or logo continuation sheets when printing letters invoices etc. and accept that anything ‘on-screen’ would be an approximation.