Thanks everyone for the input.
I bought brown ceramic eggs because that's what was available to me locally and after using them for about 2 weeks I can confirm that they still work even though my ducks lay white and gray eggs.
They always leave the ceramics on top of the real eggs but they're...
My ducks are doing the thing where they lay their eggs everywhere and change up their nests weekly so I'm thinking about getting some ceramic eggs to encourage them to lay in a few designated areas instead of anywhere that they can dig a hole.
I want to get brown or colored ceramic eggs instead...