On a seemingly unrelated note, I had no idea about the distinction between "light gray" and "light bluish gray" until yesterday; I only knew about "dark gray" and "dark bluish gray" as the pieces in those two colors tend to be bigger. So obviously, I had to go through my entire list of sets to figure out which ones may have incorrect gray pieces.
The answer was easy: all of the second-hand sets I'd bought from 2013 till now and all of my own sets from before and after the color transition in 2004 that I'd personally mashed up.
And it turns out the last sets I'd EVER mashed up in my life were the sets I used for that cringy-looking ice-based MOC in 2005.
So I opened up my Kopaka Mata, Kopaka Nuva, Kurahk and Toa Nuju to check if any of the light gray pieces were mixed up, and—of course—they were.
And now they're all in their proper places.
I literally can't believe how satisfying it was to trace and redistribute these pieces after almost 14 years.