Is there a document that explains that color chart?

This version shows different shades of colors: https://eol.jsc.nasa.gov/SearchPhotos/photo.pl?mission=AS17&...

The first one has been adjusted to bring out the contrast and saturation while the one you link is an original scan. They brought a number of different swatches like that and took a picture of a calibration array at the end to account for the effects of space exposure on the film.

The one I posted is from an original scan.

Doesn't mean it hasn't been altered before posting to juice the shadows and make it more vibrant. The one from NASA's site looks like an unaltered scan.

I think we are looking at different scans. See: https://tothemoon.im-ldi.com/about