No carrier publishes a blanket rule that every square inch of a label must be white. What they publish is a rule about the barcode, and it comes to the same thing in practice. USPS requires a package barcode to sit on substrate of uniform color and names white label stock as the suitable default; FedEx's printer troubleshooting guide says colored label stock risks failing to scan in the camera tunnel, and that a partial-color label still needs a white patch under the barcode. Both sources read 2026-08-17.
A scanner is reading the gap between the bars and whatever sits behind them, not judging your taste in paper.
Two documents, read today, cover both halves of this question. FedEx writes about the label as a printed sheet and the ways a printer ruins one; USPS writes about the barcode on it, in the standard its own scanners are built around.
| Carrier | What is published | Source |
|---|---|---|
| FedEx | “Quality labels should have solid black print on white background.” And, on colored stock specifically: “Labels printed on colored label stock might not scan in camera tunnel due to inadequate contrast”, with the fix given as using black/white contrast and, on a partial-color label, keeping “the background of the barcode” white. | fedex.com, printer maintenance guidelines |
| USPS | “Barcodes must be printed on substrate (e.g. shipping label) of uniform color”, and on the stock itself: “Typically, white label stock commonly used for barcode generation is suitable, providing it is not glossy”. This is the package barcode standard rather than general advice, so a tinted or patterned sheet fails on uniform color before contrast is measured at all. | pe.usps.com, DMM 204, sections 2.2.8 and 2.2.13 |
| UPS | No current UPS-published page we checked states a background-color rule for shipping labels in comparable terms. | not stated on the pages read |
Read the FedEx line carefully: it does not ban color everywhere on the sheet, it bans color specifically behind the barcode. A label with a colored logo block in one corner and a plain white barcode field is exactly what the guidance is describing as acceptable.
A barcode reader fires light at the label and measures how much bounces back. Black bars absorb it, the background reflects it, and the gap between the two readings is the signal. Shrink that gap with tinted stock and the reader has less to work with.
Its own guidance lists “COLOR LABEL STOCK” as a distinct cause of scan failures, filed right alongside faded thermal print and printhead dust. To the equipment, a pale-colored sheet and a worn-out printer ribbon look like the same problem.
A barcode that fails at the camera tunnel does not stop the parcel outright, but it does drop the box out of the automated sort and into somebody's hands, which is exactly the kind of delay a printed label was supposed to avoid.
You are not choosing paper stock for us. Every label an SMKlog checkout hands back is a plain black-on-white PDF straight from the carrier's own label service, so nothing here changes what you pay or how the file looks. This matters if you print through a different route, on your own colored label rolls, or through a print shop that offers tinted stock as an option.
An ordinary white sheet, printed at full size and taped down flat, meets the contrast standard by default. There is no upside to hunting for colored label rolls to save a few cents.
A colored border or logo strip around the edge of a label is fine by FedEx's own wording, so long as the barcode block itself is on white. Check that field specifically before you print a run of them.
Faint and streaked are both on FedEx's own list of scan failures, filed under voids/fading and splits. A watermark is not on that list, but it eats the same contrast the bars depend on. A second sheet costs a cent; a failed scan costs a trip back to the counter.
Not by a blanket rule at every carrier, but the part that has to work does. FedEx's own printer guidance says quality labels should have solid black print on a white background, and warns that labels printed on colored stock might not scan in the camera tunnel because of inadequate contrast. Read on fedex.com, 2026-08-17.
Because a barcode scanner reads contrast, not color. Colored stock is the one entry on FedEx's list of label problems that it blames on inadequate contrast in so many words, and the fix it gives is the black-and-white contrast of a standard labeling format. The rest of that list is printer and handling faults rather than paper. Read 2026-08-17.
You can, but keep the barcode itself on white. FedEx's guidance is explicit: if using a partial colored label, ensure that the background of the barcode remains white, and it points shippers to its standard label stock at fedex.com/us/packingsupplies rather than risk it. Read 2026-08-17.
USPS does not phrase it as a white-only rule, but its parcel barcode standard lands in the same place. DMM 204 requires barcodes to be printed on substrate, a shipping label, of uniform color, and names white label stock as what is typically suitable so long as it is not glossy. A tinted or patterned sheet fails the uniform-color test before a scanner ever measures contrast. Read on pe.usps.com, 2026-08-17.
Reprint it plain before handing it over. FedEx's troubleshooting guide does not name watermarks, but it does list faded print and white splits running through the barcode as causes of an unscannable label, and a tint works against the bars the same way. A second sheet of paper costs less than a rejected scan at the counter.
We checked UPS's current packaging and thermal-printer guidance and did not find an equivalent published statement about label background color; that row above reflects what we could and could not verify, not an assumption either way. Carriers revise these pages without notice, so a specific claim is worth confirming on the source before you rely on it.