ΔE 6.7, close: similar, with a visible difference side by side. Plague Brown is a little darker than Pure Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Plague Brown is a little darker than Pure Yellow.
The same difference applies the other way round: Pure Yellow is a little lighter.
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 Pure Yellow on the colour wheel See Plague Brown on the colour wheel
All matches: Pure Yellow equivalents · Plague Brown equivalents