So here is an idea not easily findable in the patent databases…
It seems that people serve themselves less food if it contrasts in colour with the plate they are using.
Today’s invention is therefore a bank of lights below a buffet counter. Each light is adjacent to a different tray of food.
As you pick up a serving spoon, a light comes on from beneath the counter which illuminates your transparent plate in a contrasting shade to the meal element you are choosing.
Thus each selection you make is lit in a different, contrasting colour -which limits the amount you pile onto your plate.