Brownish Decay vs Rotten Flesh

How close are they?

ΔE 7.9, close: similar, with a visible difference side by side. Rotten Flesh is more muted than Brownish Decay.

Can I use Rotten Flesh instead of Brownish Decay?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Rotten Flesh is more muted than Brownish Decay.

Can I use Brownish Decay instead of Rotten Flesh?

The same difference applies the other way round: Brownish Decay is 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.