reNightDuotone low-vision render optionproperty NightDuotonePaper: 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
clBlackPdfView1.NightDuotonePaper := clBlack;
PdfView1.Options := PdfView1.Options + [reNightDuotone];