ΔE 12.3, fair: the same colour family, but not a straight swap. Desert Olive Green is noticeably lighter, cooler than RLM 63.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Desert Olive Green is noticeably lighter, cooler than RLM 63.
The same difference applies the other way round: RLM 63 is noticeably darker, 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 RLM 63 on the colour wheel See Desert Olive Green on the colour wheel
All matches: RLM 63 equivalents · Desert Olive Green equivalents