Epson TM-C3400 Reference Manual page 178

Printing the barcode in cyan only
When the printed barcode is difficult to read, make settings to print it in cyan only.
The barcode may not be read depending on your environment. Check it before using.
1
Select [Advanced] in [Print Settings]-[Color Corrections] in [General] tab.
2
Click the [Advanced] button.
3
"Advanced" screen is displayed.
4
Select [Disable Color Correction].
5
Check [Print barcodes and 2D symbols in cyan only].
6
Click the Close] button.
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