ΔE 27.7, loose: different enough that you should pick on purpose. Mortarion Green Clear is noticeably darker, much more muted, cooler than Gladeshard.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Mortarion Green Clear is noticeably darker, much more muted, cooler than Gladeshard.
The same difference applies the other way round: Gladeshard is noticeably lighter, much 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.
See Gladeshard on the colour wheel See Mortarion Green Clear on the colour wheel
All matches: Gladeshard equivalents · Mortarion Green Clear equivalents