ΔE 6.4, close: similar, with a visible difference side by side. RLM 75 Gray is a little darker than Regiment Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). RLM 75 Gray is a little darker than Regiment Grey.
The same difference applies the other way round: Regiment Grey 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 Regiment Grey on the colour wheel See RLM 75 Gray on the colour wheel
All matches: Regiment Grey equivalents · RLM 75 Gray equivalents