Here's what google says:
Sapphire Olive Eggers start to lay beautiful olive eggs at the young age of five months old. Once they start, they will lay three to four eggs a week – over 200 per year! Despite their name, Olive Eggers don't always lay green eggs. In some cases, they can lay dark...
Your olive egger should lay a greenish-brown egg, not pastel, kind of a darker green.
The EE could lay anything from blueish to green to light brown to punkish brown.
I don't know about the Cochin or the silkie. It seems to me you need a nice brown egg layer. A RIR, a Dominique or a Barred...