Charred Bone vs Bright Brown Grey

How close are they?

ΔE 16.3, loose: different enough that you should pick on purpose. Bright Brown Grey is much more muted, warmer than Charred Bone.

Can I use Bright Brown Grey instead of Charred Bone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Bright Brown Grey is much more muted, warmer than Charred Bone.

Can I use Charred Bone instead of Bright Brown Grey?

The same difference applies the other way round: Charred Bone is much 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.