In graphic design, there’s a system for managing colour. We use the Pantone Matching System (PMS), and it it also used by printers, interior designers, and even fashion and product designers.
Each colour has a specific number so a printer will know how to add inks to create that “recipe” colour and designers will enter that number in their programs to get that colour.
If a project has only one or two colours in its design (such as stationery), then it is more cost effective to print with only one or two inks, instead of the four that make up CMYK printing process. CMYK stands for cyan, magenta, yellow and black. (Think of your inhouse printer with its four ink cartridges.) Process printing uses tiny dots made up of the four CMYK colours to create the illusion of solid colours to the eye.
With a Pantone colour, there is also a recipe of CMYK colours that will recreate it. However, the CMYK colour will not be as vibrant as a Pantone colour, due to being reproduced just with those four inks (CMYK). Metallic and fluorescent inks can also be printed using a Pantone colour.
As a logo designer, I choose Pantone inks from a specific swatch book and it’ll be a close match to a process colour to ensure consistency through all the printed material. When there’s many colours (called full colour) on the page, such as a photograph, the project will be printed as CMYK. For the design pieces that will be on the web, the colour will be changed to RGB (red, blue, green).