ΔE 14.9, fair: the same colour family, but not a straight swap. Bone Wash is noticeably lighter than Soulblight Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Bone Wash is noticeably lighter than Soulblight Grey.
The same difference applies the other way round: Soulblight Grey is noticeably darker.
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 Soulblight Grey on the colour wheel See Bone Wash on the colour wheel
All matches: Soulblight Grey equivalents · Bone Wash equivalents