ΔE 12.0, fair: the same colour family, but not a straight swap. Medium Seagray BS381C 637 is a little darker, more muted, warmer than Stormfang.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Medium Seagray BS381C 637 is a little darker, more muted, warmer than Stormfang.
The same difference applies the other way round: Stormfang is a little lighter, more saturated, 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 Stormfang on the colour wheel See Medium Seagray BS381C 637 on the colour wheel
All matches: Stormfang equivalents · Medium Seagray BS381C 637 equivalents