They might be referring to the brightly colored structural pieces. I got a batmobile, for example, that has a lot of vibrant colors for internal pieces even though the exterior is entirely black and grey. The bright colors are so the instructions are more legible (you can see what was added more readily) and can be surprising when you first open a set, but they’re fully covered in the final build and you would only know they were there if you built it yourself. The giant Imperial Star Destroyer is a great example of a model with a lot of internal color.

Pieces that should have the same color are also very inconsistent nowadays, which is especially apparent on uniformly colored areas. Ther quality control is not what it used to be. Sets like the Fiat 500 had so many pieces that didn’t match that I gave them away because I didn’t want to display them.

I switched to other manufacturers which have problems as well, but at least they are priced much lower.