When you buy a pot of paint, you effectively buy a spot colour. A mix of inks that make up a specified colour which can be used as a single-colour print.
Most common for screen printing and merchandise, these colours are universally recognised with charts such as Pantone.
Pantone colour books include swatches of colours with a unique reference number. Again, similar to handing over a colour card to a paint mixer in B&Q, the ink is mixed to match the chosen colour.
Gold, silver, metallic, and neon colours or the latex coating of a scratch card are all specified as spot colours and provide the most impact when producing vibrant colours that aren't possible through CMYK printing such as orange and greens,
Even if the production method doesn't use a spot colour, we will use a colour chart reference to configure the production method to match. Previously achieved by holding the colour swatch next to the printed item, many print machinery now match specified colours automatically.
Spot colours are often specified in logos and brand guidelines to ensure colour consistency across print and digital platforms.