Can anyone here explain me the difference between print color and layout print color?
From a brief test, objects with a layout print color assigned (either directly or by layer), will print in that color IF they reside ON the layout (i.e. NOT when they are displayed in a detail on a layout).
FWIW, I don’t use that feature (and line width) but probably would if also geometry viewed in a detail on a layout would act according to those properties…
wim has it mostly correct, where I would add to this is that it also can be applied on a per detail basis. If no details are active, then it only applies to objects on the layout, like wim stated. If you have a detail active, objects in that detail will be affected by the layer’s layout print color and weight if you change per layer layout print color / weight. If you change the print color per object, it is affected everywhere, not just in that detail.
That makes sense then. That way it works the like Layer ON/OFF works per detail. Good to know.