The best colour combination for barcode printing is black bars on a white background. However, some other combinations work as well. Bars must always be darker than the spaces. Warm colours (eg. yellow, red, orange and white) are not seen by the scanner and are therefore good for background colours. Cold colours (eg. green, blue, violet, and black) make a good choice for bars, as they appear black under red scanning light.
Metallic surfaces and inks should not be used for barcodes because they reflect light away from the scanner (this makes scanning extremely difficult). Also, a barcode should never be white bars on a black background (a reversed or ‘negative’ image) because barcode scanners can not see and decode light colours.