ΔE 9.9, close: similar, with a visible difference side by side. Regiment Grey is a little darker than F-15 Dark Grey (Mod Eagle) FS 36176.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Regiment Grey is a little darker than F-15 Dark Grey (Mod Eagle) FS 36176.
The same difference applies the other way round: F-15 Dark Grey (Mod Eagle) FS 36176 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 F-15 Dark Grey (Mod Eagle) FS 36176 on the colour wheel See Regiment Grey on the colour wheel
All matches: F-15 Dark Grey (Mod Eagle) FS 36176 equivalents · Regiment Grey equivalents