Like I said, Cayugas tend to lay BLACK covered WHITE eggs...
So... I couldn't tell you what they are without pictures.
Most Cayugas nowadays lay very little to none black over their eggs. Mine are from a hatchery, so they tend to have a light gray tinge over the shell which varies to a...
Cayugas usually have a black film on their eggs.
It may be very light, or exceptionally dark.
My mallard, Buff, and Runner ducks all lay tinted green eggs. Mallard eggs are smaller and greener than the others though.