ΔE 26.5, loose: different enough that you should pick on purpose. Ink Violet is noticeably darker, warmer than Matt Ultra Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Ink Violet is noticeably darker, warmer than Matt Ultra Blue.
The same difference applies the other way round: Matt Ultra Blue is noticeably lighter, cooler.
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 Matt Ultra Blue on the colour wheel See Ink Violet on the colour wheel
All matches: Matt Ultra Blue equivalents · Ink Violet equivalents