ΔE 8.5, close: similar, with a visible difference side by side. Plague Brown is a little darker, more muted than Warm Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Plague Brown is a little darker, more muted than Warm Yellow.
The same difference applies the other way round: Warm Yellow is a little lighter, 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.
See Warm Yellow on the colour wheel See Plague Brown on the colour wheel
All matches: Warm Yellow equivalents · Plague Brown equivalents