Page Color#

View ▸ Page Color recolors the page for comfortable reading — a dark page for a dark room, a tinted paper for a long proofreading session. It is a viewing setting, not a document edit: copying, exporting and printing all keep the document’s original colors, and your choice is remembered across launches.

Every preset keeps a WCAG AAA (7:1) contrast ratio between the ink and the paper, which is why the tints are as pale as they are.

Dark and Charcoal#

These two swap light for dark while preserving hue, so a hyperref link stays blue and a red TikZ rule stays red rather than flipping to its complement.

On macOS 26 and later, Galley hands the inversion to PDFKit itself — the same facility behind Preview’s Use Dark Appearance for PDF — which protects embedded raster images. Photographs and screenshots stay positive while the text around them turns light.

Charcoal exists for documents set entirely from the K plate. When nearly every pixel on the page is achromatic, hue preservation has nothing to preserve and Dark becomes a plain black-and-white inversion, which is harsh against a neutral paper. Charcoal warms the paper a little to take the edge off.

PDFKit classifies by drawing operator, not by intent: raster images are protected, and anything drawn as text or vector paths is inverted. A pictorial illustration exported from Illustrator is therefore inverted just like a TikZ diagram — Preview behaves identically with the same file. For design-heavy documents, reach for Sepia or Gray instead; those never invert anything.

On macOS 25 and earlier that facility does not exist, and Galley falls back to a layer filter. The fallback inverts embedded images as well, cannot set the paper color (so Charcoal looks like Dark), and rasterizes at the current zoom level rather than staying vector.

Sepia, Orange and Gray#

The paper tints are drawn as a multiply-blended overlay rather than an image filter, so glyph outlines stay vector-sharp however far you zoom in, and nothing is inverted — only the white of the paper takes the color.

System Invert Colors#

While System Settings ▸ Accessibility ▸ Display ▸ Invert colors is on, Dark and Charcoal are greyed out, so the page is never inverted twice. Toggling that system setting updates the menu without relaunching Galley.

Adjusting the dark paper#

If neither Dark nor Charcoal is the weight you want, Dark can be tuned:

defaults write com.github.munepi.galley pageColorDarkPaper "#282828"

Anything from roughly #242424 to #303030 reads as a softer dark; past that the page starts to look washed out rather than dark. Delete the key to return to the default. Colors whose relative luminance exceeds 0.10 are ignored, so light text keeps its AAA contrast ratio against the page. Charcoal is unaffected by this preference.

This is an unadvertised preference riding on a private PDFKit facility, and it exists only because the default suits some readers and not others. It may be removed or stop working in a future release of Galley or of macOS. Nothing else depends on it — if it goes away, Dark simply returns to the default paper color.

Cost when off#

With Normal selected, no layer filter is installed, no overlay layer is created, no notification observers are registered, and the document view is never forced to be layer-backed. Turning the feature off puts nothing back in the rendering path.