ΔE 9.4, close: similar, with a visible difference side by side. Transparent Sepia is a little darker, cooler than Golfag Brown. They are different kinds of paint: Citadel Golfag Brown is an opaque base/layer paint and Green Stuff World Transparent Sepia 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). Transparent Sepia is a little darker, cooler than Golfag Brown. They are different kinds of paint.
The same difference applies the other way round: Golfag Brown is a little lighter, warmer.
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 Golfag Brown on the colour wheel See Transparent Sepia on the colour wheel
All matches: Golfag Brown equivalents · Transparent Sepia equivalents