ΔE 8.8, close: similar, with a visible difference side by side. Deep Grey is a little lighter, warmer than RLM 83.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Deep Grey is a little lighter, warmer than RLM 83.
The same difference applies the other way round: RLM 83 is a little darker, cooler.
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 83 on the colour wheel See Deep Grey on the colour wheel
All matches: RLM 83 equivalents · Deep Grey equivalents