Q: Don’t suppose you know what colors can have a postnet barcode. I know that you have to stay away from shades of red, it throws off the post office scanner.
A: I spoke with a Mailpiece Design Analyst with the USPS and she said that their only guideline is “dark ink on light background.” Dark inks could include black, dark blue, dark green, etc. Light backgrounds include white, pastels, etc. You are correct that they discourage red. Their concern is that there is good reflectance on the background.