reNightDuotoneproperty NightDuotoneInk: TColor;
When reNightDuotone is present in Options, TPdfView maps rendered page luminance onto NightDuotoneInk and NightDuotonePaper before overlays are painted
Assigning this property invalidates the view immediately when reNightDuotone is active
$0000C8FF, an amber ink colour for black-paper night viewingPdfView1.NightDuotoneInk := $0000C8FF;
PdfView1.Options := PdfView1.Options + [reNightDuotone];