WWI German Grey-Green Primer vs Forest Faun

How close are they?

ΔE 8.0, close: similar, with a visible difference side by side. Forest Faun is more saturated, cooler than WWI German Grey-Green Primer.

Can I use Forest Faun instead of WWI German Grey-Green Primer?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Forest Faun is more saturated, cooler than WWI German Grey-Green Primer.

Can I use WWI German Grey-Green Primer instead of Forest Faun?

The same difference applies the other way round: WWI German Grey-Green Primer is 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.