That sounds like 'Highlight Source Markers' in the On-Screen Display Options.
It is an on screen visual only - it will not print.
There is another 'Marker Range' that just shows lines for the extents - again they won't print.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11