ΔE 9.6, close: similar, with a visible difference side by side. Light Aircraft Gray BS381C 627 is a little darker, cooler than Underhive Ash.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Light Aircraft Gray BS381C 627 is a little darker, cooler than Underhive Ash.
The same difference applies the other way round: Underhive Ash 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 Underhive Ash on the colour wheel See Light Aircraft Gray BS381C 627 on the colour wheel
All matches: Underhive Ash equivalents · Light Aircraft Gray BS381C 627 equivalents