Not all colors of paper and/or ink and type styles are compatible with automated equipment.
Inverse (or reverse) printing — i.e., light print on a dark background — is not permitted for automation and machinable mail, including BRM and QBRM pieces. Paper color is relative to the printing color of the address, barcode, return address, and postage indicia. It is very important in the barcode clear zone. The Postal Service recommends that the paper color allow the PRD (contrast) to conform to the requirements listed in the discussion on reflectance — see 11-4.
Regarding type styles and the best readability on USPS machines, the Postal Service recommends proportional or fixed fonts, or as close to proportional or fixed fonts as possible (e.g., Arial, Tahoma). Avoid script or styles similar to Gothic because USPS machines cannot read them well.
