> A more inclusive representation is to recognize a spectrum between the non-living and the living—a “grayness” resulting from the protracted evolutionary process that gave rise to life.

The meaning of "grayness" would appear to have something to do with the fuzzy line between life and non-life.

There is a footnote to the article "The Seven Pillars of Life":

https://www.pps.net/cms/lib/OR01913224/Centricity/Domain/333...

But it doesn't mention grayness at all.

This gets cleared up a little a few paragraphs in:

> The ability to clearly distinguish between abiotic and biotic systems is considered by many a prerequisite for effective astrobiology studies. However, since no natural demarcation truly exists, there is a profound difficulty in advancing the field if we rely on a strict dichotomy. ...