ΔE 8.1, close: similar, with a visible difference side by side. Mid Feldgrau is a little darker, more saturated than IJA #3 Hairanshoku (Grey Indigo).
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Mid Feldgrau is a little darker, more saturated than IJA #3 Hairanshoku (Grey Indigo).
The same difference applies the other way round: IJA #3 Hairanshoku (Grey Indigo) is a little lighter, more muted.
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 IJA #3 Hairanshoku (Grey Indigo) on the colour wheel See Mid Feldgrau on the colour wheel
All matches: IJA #3 Hairanshoku (Grey Indigo) equivalents · Mid Feldgrau equivalents