ΔE 10.2, fair: the same colour family, but not a straight swap. Light Sea Gray is a little darker, cooler than Fenrisian Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Light Sea Gray is a little darker, cooler than Fenrisian Grey.
The same difference applies the other way round: Fenrisian Grey is a little lighter, warmer.
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 Fenrisian Grey on the colour wheel See Light Sea Gray on the colour wheel
All matches: Fenrisian Grey equivalents · Light Sea Gray equivalents