ΔE 16.4, loose: different enough that you should pick on purpose. Interference Green (Fine) is noticeably lighter than Mithril. They are different kinds of paint: Army Painter Mithril is a metallic and Golden Interference Green (Fine) is a pearl paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Interference Green (Fine) is noticeably lighter than Mithril. They are different kinds of paint.
The same difference applies the other way round: Mithril is noticeably darker.
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 Mithril on the colour wheel See Interference Green (Fine) on the colour wheel
All matches: Mithril equivalents · Interference Green (Fine) equivalents