Dark Wood vs Demon Brown

How close are they?

ΔE 17.1, loose: different enough that you should pick on purpose. Demon Brown is a little lighter, more saturated, cooler than Dark Wood.

Can I use Demon Brown instead of Dark Wood?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Demon Brown is a little lighter, more saturated, cooler than Dark Wood.

Can I use Dark Wood instead of Demon Brown?

The same difference applies the other way round: Dark Wood is a little darker, more muted, 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.