ΔE 19.3, loose: different enough that you should pick on purpose. Dirty Grey is noticeably lighter, more saturated, cooler than Green Brown.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Dirty Grey is noticeably lighter, more saturated, cooler than Green Brown.
The same difference applies the other way round: Green Brown is noticeably darker, 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 Green Brown on the colour wheel See Dirty Grey on the colour wheel
All matches: Green Brown equivalents · Dirty Grey equivalents