ΔE 16.9, loose: different enough that you should pick on purpose. Death Korps Drab is noticeably lighter than RAL 6003 Olivgrün opt.2.
Can I use Death Korps Drab instead of RAL 6003 Olivgrün opt.2?
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Death Korps Drab is noticeably lighter than RAL 6003 Olivgrün opt.2.
Can I use RAL 6003 Olivgrün opt.2 instead of Death Korps Drab?
The same difference applies the other way round: RAL 6003 Olivgrün opt.2 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.