A ‘Spot colour’ is exactly what it suggests – almost! It is usually an additional printed colour on top of the standard 4 inks that make up offset/litho printing.
This process uses the four colours, cyan magenta, yellow and black but some advanced processes use orange and green to reproduce faint tints that can not always be obtained by just the cmyk range. (Hexachromatic process or CMYKOG).
A spot colour is a non standard colour usually specified to the Pantone Matching System, it can be metallic or fluorescent or even custom hand mixed. It is also a term used when a spot varnish is required. This can be lamination or ‘UV’ coatings.
Each colour ink in the printing process has to have a lithographic film and plate to print and produce the correct colours, a spot varnish also requires a separate film and plate so is counted as a ‘spot colour’.
In most cases a ‘spot colour’ will be added if there is a special colour required that has to match a particular branding or house colour. Many large companies have very strict rules and it is essential to keep the exact consistency throughout all their literature where ever it is printed.
A spot colour is used when accuracy is critical, especially for small text and graphics. When there are only a couple of colours required it is often more cost effective to print with two or three spot colours rather than use the four colour process. Stationery is a prime example – using a spot colour – a specified pantone colour and black. The printer only has two processes rather than 4 and can achieve the same or an improved result.
Problems can occur when a spot colour is used in a graphic file and is not converted to the four colour CMYK standard. When this accidentally happens the file will be output with an extra plate which has not been allowed for and will increase costs. Some software will flag up an alert so it can be corrected or approved.
Spot colours, when used in a CMYK document will not always convert to the colour expected so colour proofing may be necessary.
Don’t choose a colour based on your monitor unless calibrated carefully but it still will have limitations for previewing colour. A screen image will never print as you see it.
Finally always check with your printer what the extra cost will be for printing a spot colour – it can make a huge difference! You also must make sure they have the capacity to print ‘5’ colours at one time which will also make a difference to the cost.