ΔE 11.4, fair: the same colour family, but not a straight swap. Buff is noticeably lighter, warmer than Charred Bone.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Buff is noticeably lighter, warmer than Charred Bone.
The same difference applies the other way round: Charred Bone is noticeably darker, 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 Charred Bone on the colour wheel See Buff on the colour wheel
All matches: Charred Bone equivalents · Buff equivalents