IJA #21 Midori iro (Green) vs Deep Green

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Deep Green is more saturated, cooler than IJA #21 Midori iro (Green).

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

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Deep Green is more saturated, cooler than IJA #21 Midori iro (Green).

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

The same difference applies the other way round: IJA #21 Midori iro (Green) 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.