> What are the CIE XYZ coordinates of each colored square?

In the most expensive versions, they measure each individual patch, in case printing imperfections make the colours slightly different. And of course because you can’t get the exact same inks when a product is 50 years old!

> How were the colors chosen?

Skin and foliage; primary colours; greyscale; and miscellaneous.

They also make a 140 colour patch version - the “ColorChecker Digital SG” - that provides more coverage; 14 different skin tones instead of 2 for example!