ΔE 12.5, fair: the same colour family, but not a straight swap. Caliban Green is a little darker, cooler than Dunkelgrün RLM 81.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Caliban Green is a little darker, cooler than Dunkelgrün RLM 81.
The same difference applies the other way round: Dunkelgrün RLM 81 is a little lighter, 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 Dunkelgrün RLM 81 on the colour wheel See Caliban Green on the colour wheel
All matches: Dunkelgrün RLM 81 equivalents · Caliban Green equivalents