ΔE 12.0, fair: the same colour family, but not a straight swap. RLM 83 Dark Green is a little lighter, more muted, cooler than Lupercal Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). RLM 83 Dark Green is a little lighter, more muted, cooler than Lupercal Green.
The same difference applies the other way round: Lupercal Green is a little darker, 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 Lupercal Green on the colour wheel See RLM 83 Dark Green on the colour wheel
All matches: Lupercal Green equivalents · RLM 83 Dark Green equivalents