ΔE 11.5, fair: the same colour family, but not a straight swap. Grey Seer is a little lighter, more muted than RLM 65 (1938).
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Grey Seer is a little lighter, more muted than RLM 65 (1938).
The same difference applies the other way round: RLM 65 (1938) is a little darker, more saturated.
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 65 (1938) on the colour wheel See Grey Seer on the colour wheel
All matches: RLM 65 (1938) equivalents · Grey Seer equivalents