Beside Automatic, the Themes dialog's colour picker offers Theme: the page's
section's hue at a fixed shade, grey for a grey section and OneNote's blue for
none. Pages store the resolved colour, so OneNote 2010 draws it; themes.json keeps
"accent": true beside the uncoloured section's colour, which versions without the
flag take. Every writer resolves from the section colour in the shared files, so
users agree and a page restyles only when its section's colour changes.

Assisted-by: claude-opus-5.5