I believe the reason for this strange color scheme is the lack of a revision control system. Back in the dark ages of programming, we didn’t use them. We edited

I believe the reason for this strange color scheme is the lack of a revision control system. Back in the dark ages of programming, we didn’t use them. We edited files on disk, and that was that. In that environment, a deletion is dangerous. If you decide you want it again after you delete it, well, that’s tough. I don't think this explanation makes any sense. What was this person from the dark ages diffing against? Presumably, something on disk (i.e. something whose contents are recoverable).