As best as can be discerned from a few old pre-digital pictures the original gym shirts are an extremely close match to the shirt vendor's Ice Grey color. (If by some small chance someone has a old shirt around, I'd cover postage to see it and get a more accurate color appraisal).
Ice Grey is not available for the women's cut shirt. For maximum authenticity I suggest ordering a men's shirt. If a women's cut is desired the two color options worthy of consideration are white or a grey somewhat darker than the original shirts called Sports Grey.
Examples of the colors are below. When ordering a women's cut shirt there is a place on the order form to specify which of the two colors (white or sports grey) is preferred. I will not be doing both colors but rather all women's cut shirts will be in the one color preferred by the most people ordering them.