From the EFF website(1), you can learn this:
"(Added 2017) Reminder: it appears likely that all recent commercial color
laser printers print some kind of forensic tracking codes, not necessarily
using yellow dots. This is true whether or not those codes are visible to the
eye and whether or not the printer models are listed here. This also includes
the printers that are listed here as not producing yellow dots."
You get tracked through the documents you print, in the sense that they can
be traced to your printer's serial number, and hence to you if you have
somehow registered it or if can be associated to another document you printed
using the same printer.
This does not apply to inkjet printers or to watercolor paintings, except of
course if you sign them.
I still like the idea of being able to hide the picture of a cat in the
picture of a tree.
(1)
https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots
