ΔE 9.4, close: similar, with a visible difference side by side. Siena is a little lighter, more saturated than Camo Brown. They are different kinds of paint: Army Painter Camo Brown is an opaque base/layer paint and Green Stuff World Siena is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Siena is a little lighter, more saturated than Camo Brown. They are different kinds of paint.
The same difference applies the other way round: Camo Brown is a little 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.
See Camo Brown on the colour wheel See Siena on the colour wheel
All matches: Camo Brown equivalents · Siena equivalents