ΔE 7.8, close: similar, with a visible difference side by side. Luftwaffe Green is more muted, cooler than RAL 6003 Olivgrün opt.2.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Luftwaffe Green is more muted, cooler than RAL 6003 Olivgrün opt.2.
The same difference applies the other way round: RAL 6003 Olivgrün opt.2 is 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 RAL 6003 Olivgrün opt.2 on the colour wheel See Luftwaffe Green on the colour wheel
All matches: RAL 6003 Olivgrün opt.2 equivalents · Luftwaffe Green equivalents