ΔE 10.6, fair: the same colour family, but not a straight swap. Ivory is noticeably lighter than Terminatus Stone.
Can I use Ivory instead of Terminatus Stone?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Ivory is noticeably lighter than Terminatus Stone.
Can I use Terminatus Stone instead of Ivory?
The same difference applies the other way round: Terminatus Stone is noticeably darker.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.