ΔE 8.8, close: similar, with a visible difference side by side. Interior Grey Green is a little darker, more saturated, cooler than Ruins Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Interior Grey Green is a little darker, more saturated, cooler than Ruins Grey.
The same difference applies the other way round: Ruins Grey is a little lighter, more muted, 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 Ruins Grey on the colour wheel See Interior Grey Green on the colour wheel
All matches: Ruins Grey equivalents · Interior Grey Green equivalents