If the background is white, it’s already possible: https://simplepdf.eu/help/faq/how-to-add-background

For other colors, it’s in the backlog!

(I’d aiming to automatically provide the correct color by inspecting pixels within the area to redact, to make it as simple as possible)

Yeah but hiding the information versus removing it is two different things. By hiding it, the information is still there but hidden.