Highlighting with white/black color hides the text - black highlights hide black text in regular viewing, while white highlights hide the text when document colors are replaced with white text on black background.

Instead, it might be useful for black highlights to have the text displayed as white text over the highlight, while white highlights have a black border around the text in regular viewing, and vice versa for when document colors are inverted (ie, white text showing over black and white highlights with a white border around the highlight).

This would allow for visual separation of black/white highlights from redaction, regardless of the warning given when using these highlights.