Indian Runner Laying Black eggs

[Gone-Quackers]

I've got several different colors of runners and am amazed that one of my ducks is laying black eggs. In this photo it doesn't look really black but in real life it's really, really black- especially the pointy end.
So what color of runner lays black eggs? I have hens in the following colors: fawn/white, blue/white, chocolate/white, mallard, apricot/white, and lavender.

Thanks for any help! Google just isn't helping me. . neither is Storey's Guide to ducks

 

[Amiga]

I have black and chocolate Runners. A few times, when they started to lay, there have been eggs with so much bloom on them that they are nearly black. Underneath they were the pale blue-green that I am used to.

 

[Gone-Quackers]

I have black and chocolate Runners. A few times, when they started to lay, there have been eggs with so much bloom on them that they are nearly black. Underneath they were the pale blue-green that I am used to.

Yes, today I got another egg except it was more gray than black. I scraped a bit off and it was blue-green underneath. I suspect it's my blue runner providing such colorful eggs as it's a very dark blue runner -- perhaps only has 1 dilution factor so eggs are darker than they might otherwise be?