Scanners read bar code by recognition of the contrast between light and dark areas of the symbol. Light colours (white, yellow and “warm” colours such as read and orange) are suitable for the background and light margin areas. Dark colours (black, blue and green) are suitable for the bars. This means that although black and white are obviously the safest contrasting colours, other colours can be equally effective and may complement the pack design.
A scanner “reads” the bar code symbol by means of a red light source, so what the scanners “sees” is quite different to what human eye sees. As such, although many colour combinations are clearly visible to the eye, some bar codes will scan and some bar codes will not.
Whatever colours are chosen, it is very important for manufacturer to discuss their bar coding programme with their printer. The printer is the best person to advise on suitable colours because he has the experience of how inks and other factors can affect print qualitu and, therefore, the quality of the printed bar code.
Source: GS1 Malaysia
