What is Duck Egg Blue?

This gorgeous Mallard duck is nesting in my flower bed. I discovered it on Sunday.  This female and her mate often stop by to swim in my pool. This year they decided to nest here. The gestation period is 21-28 days. On Sunday after discovering it, she left the nest and there were no visible eggs, again today, I didn't see any eggs. Maybe she covers them up when she leaves, I don't know. I will keep you posted. I'm curious to see what color "duck egg blue" really is