> Black text on white background (#000 on #fff) used to be standard on computer displays
Aside from computers with built in (e.g., early Macs) or external TV-style displays that had no color support (e.g., Timex Sinclair 1000), and later Macs even though they had color support, that doesn't seem to have ever been common, even on other machines of the same time.
EDIT: It was common on word processing, desktop publishing, and some other apps once WYSIWYG became a big trend, but that was pretty explicitly about print-on-white-paper skeumorphism, not an idea of what was ideal for work on a computer outside of the specific context of mirroring what print would look like.
Aside from computers with built in (e.g., early Macs) or external TV-style displays that had no color support (e.g., Timex Sinclair 1000), and later Macs even though they had color support, that doesn't seem to have ever been common, even on other machines of the same time.
EDIT: It was common on word processing, desktop publishing, and some other apps once WYSIWYG became a big trend, but that was pretty explicitly about print-on-white-paper skeumorphism, not an idea of what was ideal for work on a computer outside of the specific context of mirroring what print would look like.