Color Print Markings On Sheet Margins

Hey folks,
I have seen some sheets of stamps that come either with or without color print markings on the margins. Does this mean that they belong to different print batches? Is there any other significance to it?

Below I am attaching pictures of a 1979 example from the DDR, and an example of a recent joint issue from Italy and the Vatican City where both sheets can be found either with or without such color print markings.

A printer's (Druckbogen in German) sheet, normally, is much larger than are these sheets. They are sheets from different positions in the printer's sheet. The printer's sheet was then cut into counter sheets (Schalterbogen).

Very common, Australia see "Traffic Lights"

Used to confirm colour intensity and registration of the colour plates.

Some have fabulous Marginal Markings See Hungary "Horses and riders"

Paolo, with the first sheets (Faience) the colour markings are still on the lower sheet, (see colour lines)
This assists the inspector, to quickly identify if a colour is missing, or not.

Saves looking at all the stamps individually.

Thanks both for your replies.

NSK, your explanation is very interesting. However, if the color markings were only to be found one time per each "Druckbogen", there would just a few "Schalterbogen" with such markings and many more without them, for each stamp type. At least for the posted joint issue, however, that doesn't seem to be the case, as the number of sheets with and without color markings on the market seems to be abot the same.

Rod, I know the function of these markings, but I was trying to understand why they wouldn't be present on all sheets from the same print run... Coincidentially, I also collect comic books and have seen the same thing happening, where some copies of a specific comic book from the 1970s feature a crosshair print mark on the cover and other copies don't.

Right, OK
so how about, your reference to "sheets" ?
These appear to be "panes"
Perhaps the markings appear on every sheet, but not on every pane?

Yes, that is also what NSK said initially.
That might very well be the case.

The edges of the panes sometimes have these color markings. As was explained, it is easier to spot a missing color. Since sheets contain multiple panes, it's a waste of paper (and ink) to have this on all panes. The panes with markings often land at the philatelic bureau and the ones without are usually for daily consumption at the counters. My preference is WITH markings. Those you show are beautiful. Thanks.

I guess the infamous "Traffic Light Gutter Pair" craze has never fully disappeared.