Hey, just wanted to mention a really cool free app I picked up that I think could help with working on egg color.
It's Color Grab on Android (and I'm sure there are a ton of others that do the same, as well as for other devices). Grabs the RGB/Hex/HSV values from your camera, which means you can easily and objectively look at egg color. I tried one of the paper charts to compare against, but human eyes are just not so great at determining the small color differences. I am going to set up a consistent good lighting spot to take my readings from, but for now it's just a good offhand reference.
Here's some examples from the eggs collected today: 3 Pattens Blue (#D3EEF6), 1 Onahau (#C3E3D3), 1 Jagged Ice ($C8E1E0), 1 Iceberg (#CBE0E0) and 1 very off color Zumthor (#C1D9D4).
Figured I'd share it in case anyone else might find it useful!