Scanners look for clear contrast between the bars and spaces in order to decode a barcode. If the contrast isn’t sufficient, the barcode won’t scan. The best combination of colours for a barcode is black bars on a white background. Other combinations can be used but it’s important to follow guidelines: Barcodes must be printed so that the dark bars (black, dark green, dark blue for example) appear against a light background.

It is not possible to read a barcode if it is reversed; that is, printed with light bars against a dark background.

It is not always necessary to introduce black as an extra colour if one of the colours that already exists in the design appears black under a red light.

If you’re using a semi-transparent substrate (surface), do not rely on the colour of the contents of the packaging to provide a background colour.

Typically, scanners use red light to detect the contrast between the bars and spaces to it’s important that red, including reddish colours like brown, are not used as doing so will make the bars invisible to the scanner’s red light.

I’m a good packaging printer and one of the most important checks are barcode scan checks.