Don't use color printers. You don't need them and they're gay. If you want color, paint stuff with sharpies.
Buy an old BlackWhite laserprinter like the old kyocera FS-1020d, or something for 30$. Not only are those really excellent printers, they also can only print black dots, which can easily be spotted with magnifying classes. That makes hiding a tracking code very hard, so there probably is none. As they have very old-style large toner containers, you also can be sure, that there's nothing but black toner in the printer.
Newer BW printers use toner containers, which theoretically could hide some small container with less-visible ink/toner for adding a tracking code, but the old ones made for businesses can't. Their toner cartridges are refillable and only slightly more complex than a waterbottle.
I'd also like to mention, that everything leaves physical traces, which can be found by forensics. They probably can even prove with which sharpie you painted the funny-looking swastika. But it's a huge difference, whether they get a nice encoded serial number, or just some random blotch with slightly unique characteristics.
Also think about making QR code stencils for spraypainting. You'd have to make several stencils per QR-code, and spraypaint only parts of the code with every stencil, but if you work cleanly, and align the templates right, it's possible to spraypaint QR codes. Cutting the stencils is work, but it's doable.