ΔE 22.3, loose: different enough that you should pick on purpose. Green Ghost is noticeably darker, cooler than Garaghak's Sewer.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Green Ghost is noticeably darker, cooler than Garaghak's Sewer.
The same difference applies the other way round: Garaghak's Sewer is noticeably 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 Garaghak's Sewer on the colour wheel See Green Ghost on the colour wheel
All matches: Garaghak's Sewer equivalents · Green Ghost equivalents