Docspress uses one accent color, soft rules, and generous white space because a document site already has a strong visual subject: the text and the relationships between its sections.
The sidebars are maps. The article is the place. The page TOC is a local index. When these layers compete equally, reading becomes interface management. When they keep their roles, orientation becomes almost invisible.
That balance is the design test for future features: does this help the reader locate, understand, or continue the document? If it does none of those things, it probably does not belong in the core theme.