The EFF document "List of Printers Which Do or Do Not Display Tracking Dots" has (update 2017). It mentions it's not necessarily yellow dots and it appears like

The EFF document "List of Printers Which Do or Do Not Display Tracking Dots" has (update 2017). It mentions it's not necessarily yellow dots and it appears likely that some sort of forensic tracking code is used on all printers. https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots https://www.eff.org/pages/list-printers-which-do-or-do-not-d...