ΔE 19.5, loose: different enough that you should pick on purpose. Marine Blue is a little darker, more saturated, warmer than Frostveil.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Marine Blue is a little darker, more saturated, warmer than Frostveil.
The same difference applies the other way round: Frostveil is a little lighter, more muted, 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 Frostveil on the colour wheel See Marine Blue on the colour wheel
All matches: Frostveil equivalents · Marine Blue equivalents