On this website you will often see finish descriptions of cloth described as "in the greige" where "greige" is pronounced the same as the color "Gray" but has nothing to do with color. If you google the word "Greige" it appears it has been hijacked by the color namers that claim that Greige is mix of Gray and Beige. I can't believe they did that and weren't even aware the word is a real word used to refer to cloth still in the loom state.
So what is greige when it refers to fiberglass cloth? It means that the cloth has not been finished. When fiberglass cloth is woven, in the US anyway,
it has a water soluble Poly Vinyl Alcohol coating that makes the glass yarn slippery so it doesn't break during weaving. The weight percentage is in the 1 - 2% range. The look and feel of cloth at this stage is very distinct. It has a slippery feel to it. It also has a distinct smell. Fiberglass Cloth used in Silicone Rubber coating is left at this stage as the companies I know prefer fiberglass cloth in the greige.
For anyone using fiberglass cloth in composites and many other applications the pva is heated, washed, water washed, carmelized and finished in a variety of ways to become compatible with whatever resin or matrix is to be added later.