PDFs showing in black background

[worldor]

Hi

PDFs showing in black background, is this how the actual PDFs are or a Sumatra issue or settings thing?

Thank you

[GitHubRulesOK]

Default for most PDF viewers is PER standard White paper on one colour but each viewer can decide how to colour the surround so SumatraPDF has a few over-rides for the BLACKground but always uses Black for presentation background but user colours for Full screen.

Just be cautious as it can get very confusing using odd settings

[kjk]

Most likely you accidentally enabled Invert Mode.
To toggle press i (in 3.5.2 or earlier) or Shift + i in pre-release and 3.6+