ΔE 65.4, loose: different enough that you should pick on purpose. Gloss Varnish is noticeably lighter, much more muted than Mordant Earth.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 65). Gloss Varnish is noticeably lighter, much more muted than Mordant Earth.
The same difference applies the other way round: Mordant Earth is noticeably darker, much 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 Mordant Earth on the colour wheel See Gloss Varnish on the colour wheel
All matches: Mordant Earth equivalents · Gloss Varnish equivalents