Doombull Brown vs Walnut Brown

How close are they?

ΔE 16.1, loose: different enough that you should pick on purpose. Walnut Brown is a little darker, much more muted than Doombull Brown.

Can I use Walnut Brown instead of Doombull Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Walnut Brown is a little darker, much more muted than Doombull Brown.

Can I use Doombull Brown instead of Walnut Brown?

The same difference applies the other way round: Doombull Brown is a little lighter, much more saturated.

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.