property Color: TColor; // published, inherited from TControl
Color fills the area of the viewer client rectangle that lies outside the page artwork — the margin between consecutive pages, the area around the document when it is narrower than the viewport, and any region revealed by aggressive scrolling. Together with PageColor, PageBorderColor and PageShadowColor it determines the overall look of the reader.
The most common dark-mode reader effect is achieved by setting Color := clBlack (or a deep grey such as $303030) and keeping PageColor light so the paper still appears bright. For a printed-page metaphor leave Color at its default and add a non-zero PageShadowSize to give each page a drop shadow against the background.
The colour is also visible during the brief moment a page is still being rasterised by PDFium — before the first bitmap is available the viewer paints LoadingColor on top of Color, then replaces it with the rendered page bitmap once it arrives.
clBtnFace from the inherited declaration; assign explicitly for a predictable look across themes.PageColor and is replaced by document content once the page renders.Color with PageBorderColor for a clear separation between the page area and the surrounding background, especially when the page background is also dark.
// Configure a soft dark-mode reader
procedure TForm1.ApplyDarkTheme;
begin
PdfView1.Color := $202020;
PdfView1.PageColor := clWhite;
PdfView1.PageBorderColor := $404040;
PdfView1.PageShadowColor := $101010;
PdfView1.PageShadowSize := 6;
PdfView1.LoadingColor := $202020;
PdfView1.Invalidate;
end;