ΔE 28.6, loose: different enough that you should pick on purpose. Bismark's Grave is noticeably darker, much more muted than Arctic Gem.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Bismark's Grave is noticeably darker, much more muted than Arctic Gem.
The same difference applies the other way round: Arctic Gem is noticeably lighter, 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 Arctic Gem on the colour wheel See Bismark's Grave on the colour wheel
All matches: Arctic Gem equivalents · Bismark's Grave equivalents