ΔE 11.3, fair: the same colour family, but not a straight swap. Plague Brown is a little darker, more saturated, warmer than Yellow FS33531.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Plague Brown is a little darker, more saturated, warmer than Yellow FS33531.
The same difference applies the other way round: Yellow FS33531 is a little lighter, more muted, cooler.
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 Yellow FS33531 on the colour wheel See Plague Brown on the colour wheel
All matches: Yellow FS33531 equivalents · Plague Brown equivalents