ΔE 23.5, loose: different enough that you should pick on purpose. Green Brown is noticeably lighter, much more saturated, cooler than Dark Mud.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Green Brown is noticeably lighter, much more saturated, cooler than Dark Mud.
The same difference applies the other way round: Dark Mud is noticeably darker, much more muted, 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 Dark Mud on the colour wheel See Green Brown on the colour wheel
All matches: Dark Mud equivalents · Green Brown equivalents