Dryad Bark vs Burnt Sienna Umber

How close are they?

ΔE 8.6, close: similar, with a visible difference side by side. Burnt Sienna Umber is more saturated than Dryad Bark.

Can I use Burnt Sienna Umber instead of Dryad Bark?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Burnt Sienna Umber is more saturated than Dryad Bark.

Can I use Dryad Bark instead of Burnt Sienna Umber?

The same difference applies the other way round: Dryad Bark is 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.