ΔE 15.6, loose: different enough that you should pick on purpose. Dark Vermilion is a little darker, much more muted than Crimson.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Dark Vermilion is a little darker, much more muted than Crimson.
The same difference applies the other way round: Crimson is a little 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 Crimson on the colour wheel See Dark Vermilion on the colour wheel
All matches: Crimson equivalents · Dark Vermilion equivalents