ΔE 18.9, loose: different enough that you should pick on purpose. Mortarion Green Clear is noticeably darker, more muted than Gauss Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Mortarion Green Clear is noticeably darker, more muted than Gauss Green.
The same difference applies the other way round: Gauss Green is noticeably lighter, 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.
See Gauss Green on the colour wheel See Mortarion Green Clear on the colour wheel
All matches: Gauss Green equivalents · Mortarion Green Clear equivalents