Codex has a rather large list of border colours to choose from (10 of which are shades of grey): https://doc.wikimedia.org/codex/latest/design-tokens/border.html
VE uses some colours from the old design guide that are no longer on that list, specifically #eaecf0 / color.gray100:
| Separator between multiple context items on desktop & mobile, and link label | |
| Close button separator on mobile toolbar | |
| Horizontal separators between head/body/foot on mobile | |
| Symbol list button borders. Fixed in T406982 | |
| Add new image button in gallery dialog | |
The lightest grey allowed now is #dadde3 / color.gray200 / border-color-muted, although that is currently unused in VE. In many places we are using #c8ccd1 / color.gre300 / border-color-subtle for internal borders (e.g. desktop toolbar separators, visual diff sidebar).




