[Unclenick]

If the grey is on the case body below the annealed area, if the atmosphere in their location gets humid enough, and especially if there are chemical vapors in it, you can get oxidation of the zinc in the brass, whose oxide is white, and then also get black copper oxide forming. The right mix of the two colors could conceivably look grey, though when I've seen oxidation damage with both oxides, it usually is black center areas surrounded by a white collar.

My approach would be to tumble the brass with polish to see if the color returns. If it looks normal afterwards, do a load workup from a low minimum, like the Hornady manual often has, using a handful of cases randomly selected from the group, watching for splitting along the way. If you get any splits, toss the lot, as zinc oxidation has tunneled too deeply and weakened it. If it holds up, do several reloads to make sure none appear. If they don't, you are likely good to go with the rest, though I would still inspect for splits with a little extra after each firing.