Is there any documentation from Microsoft's side about the terms to use?
No, other than the class-part-state scheme. I doubt Microsoft will name all the colors in modern themes. The most probable way would be that those graphic designers use a set of colors as the palette/UI guideline for a theme so the user experience is consistent. For classic themes, there are things like EDGE_RAISED, EDGE_SUNKEN, EDGE_ETCHED, BDR_RAISED, etc. However, I don't think they will be useful for modern themes. Because these theme parts are basically bitmaps. For example, how do you name all the colors in a theme with skeuomorphic icons? For the light theme, as I am not a graphic designer and I was lazy, so I designed those icons with bare rounded corners and no complex effects. That's why there are usually just the fill and stroke colors for those icons with a palette consisting of mainly different blue colors.