Garaghak's Sewer vs Forest Green

How close are they?

ΔE 26.7, loose: different enough that you should pick on purpose. Forest Green is noticeably darker, more muted, cooler than Garaghak's Sewer.

Can I use Forest Green instead of Garaghak's Sewer?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Forest Green is noticeably darker, more muted, cooler than Garaghak's Sewer.

Can I use Garaghak's Sewer instead of Forest Green?

The same difference applies the other way round: Garaghak's Sewer is noticeably lighter, more saturated, 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.