ΔE 43.4, loose: different enough that you should pick on purpose. Ink White is noticeably lighter, much more muted than Sapphire Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 43). Ink White is noticeably lighter, much more muted than Sapphire Blue.
The same difference applies the other way round: Sapphire Blue is noticeably darker, much more saturated.
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.
See Sapphire Blue on the colour wheel See Ink White on the colour wheel
All matches: Sapphire Blue equivalents · Ink White equivalents