IJA #21 Midori iro (Green) vs Luftwaffe Green

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Luftwaffe Green is a little darker, warmer than IJA #21 Midori iro (Green).

Can I use Luftwaffe Green instead of IJA #21 Midori iro (Green)?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Luftwaffe Green is a little darker, warmer than IJA #21 Midori iro (Green).

Can I use IJA #21 Midori iro (Green) instead of Luftwaffe Green?

The same difference applies the other way round: IJA #21 Midori iro (Green) is a little lighter, 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.