ΔE 16.4, loose: different enough that you should pick on purpose. Caliban Green is a little lighter, more saturated, warmer than Mecha Dark Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Caliban Green is a little lighter, more saturated, warmer than Mecha Dark Green.
The same difference applies the other way round: Mecha Dark Green is a little darker, more muted, cooler.
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 Mecha Dark Green on the colour wheel See Caliban Green on the colour wheel
All matches: Mecha Dark Green equivalents · Caliban Green equivalents