Glad I could share this tidbit.
What led me down this path of discovery was the fascination with the subtle differences in a few shades of gray, blue, and silver that occured in the mid to late 90s. Like when BMW used Aspen & Arctic Silver on the early e38s then dropped them and went to Titanium Silver. I noticed that the Arctic Silver had a bluish undertone, and the Aspen Silver had a lavender undertone...then the Titanium was whiter as if it had a light silver or white undertone. While looking at the color labels, I noticed the other color in lower case letters...which really sparked my curiosity as to what it meant.
The undercoat revelation opened my eyes to the depth & sublte difference BMW could get in having several shades of silver, blue, green, gray, red, and browns/tans. Especially the colors like Stratus Gray that are kind of camelion-like and can look totally different based on the type of light it's seen in.