For example, British milk sellers mostly use the same shared milk container, with different labels.
They figured out how to lower the cost, because they were paying for it. They get really in depth in the specific amounts of dye to use in lids etc. to maximise recycling.
https://wrap.org.uk/resources/report/hdpe-milk-bottle-resear...
None of that needed specific regulations, just assigning the costs to the people responsible.