ΔE 7.2, close: similar, with a visible difference side by side. Dark Drab is a little darker than RLM 73.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Dark Drab is a little darker than RLM 73.
The same difference applies the other way round: RLM 73 is a little lighter.
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 RLM 73 on the colour wheel See Dark Drab on the colour wheel
All matches: RLM 73 equivalents · Dark Drab equivalents