Short answers, pulled from the story.
The first recorded use of the word grey as a color name in the English language appeared in the year 700 CE. This linguistic milestone predates the modern distinction between the spellings grey and gray by nearly a millennium.
Cistercian monks and friars of the Franciscan and Capuchin orders wore grey to signify their rejection of worldly wealth and to symbolize their vows. This association with humility and poverty made the color a visual marker of their social status and economic hardship.
Rembrandt van Rijn created warm greys by mixing black pigments derived from charcoal or burnt animal bones with lead white. He would further warm these greys with a little red lake color from cochineal or madder to achieve incredible subtlety of pigmentation.
The Confederate Army wore grey uniforms because the South lacked a major dye industry and grey dyes were inexpensive and easy to manufacture. Nicola Marschall, a German-American artist who designed the original Confederate flag, created the cadet grey uniform that became the standard for the Confederate Army.
A team of Harvard scientists suggested in the February 2005 issue of Science that hair turns grey due to the failure of the melanocyte stem cells to maintain the production of essential pigments. This biological process occurs when the melanocyte stops injecting melanin into the hair cells.
The grey goo scenario describes out-of-control self-replicating nanobots that consume all living matter on Earth. This hypothetical situation represents the potential dangers that come with the technological age and the use of grey in the field of nanotechnology.