In brief
Vox Liberata starts with the device's colour setting. A reader who chooses Light or Dark can keep that setting when moving from the homepage to the build log. The choice is stored in that browser and the privacy page explains what is saved.
Read the choice before drawing the page
The page reads the saved choice before it draws the first frame. That gives the stylesheet the right colours at the start and reduces the flash that can occur when a page switches colours after loading. Returning to Auto removes the explicit choice and puts the device back in charge.
Keep the control working when storage is blocked
The control applies the choice to the open page even when the browser refuses to save it. A check with storage disabled verified that the control still changes the displayed colours. Persistence depends on the reader's browser allowing the save.
The public-page build step reapplies the colour control after generation. It uses the same enhancement pass as the rotating homepage photographs, but a reader's colour choice is independent of the selected photograph.