Read from the shape's JSON, which is the model: the accessors cover only its type, text and adjust values. A fill or line the shape does not state is named by where it comes from (its theme style) rather than resolved to a color — the theme is the workbook's, and the report says which reference to follow.
The facts of a shape a report states beyond its placement: what it is, what it says, how it is drawn, what it links to and what it is glued to. Each fact only where the shape states it or it is not the default, so a plain rectangle stays a few lines.