RLM 81 Version 3 vs Eshin Grey

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Eshin Grey is a little darker, more muted than RLM 81 Version 3.

Can I use Eshin Grey instead of RLM 81 Version 3?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Eshin Grey is a little darker, more muted than RLM 81 Version 3.

Can I use RLM 81 Version 3 instead of Eshin Grey?

The same difference applies the other way round: RLM 81 Version 3 is a little lighter, 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.