Dark Wood vs Desert Ochre

How close are they?

ΔE 17.4, loose: different enough that you should pick on purpose. Desert Ochre is noticeably lighter, more saturated than Dark Wood.

Can I use Desert Ochre instead of Dark Wood?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Desert Ochre is noticeably lighter, more saturated than Dark Wood.

Can I use Dark Wood instead of Desert Ochre?

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

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.