IJA #1 Hairyokushoku (Grey-Green) vs USAAF Light Gray

How close are they?

ΔE 4.0, very close: most people won’t see a difference side by side. USAAF Light Gray is a little lighter than IJA #1 Hairyokushoku (Grey-Green).

Can I use USAAF Light Gray instead of IJA #1 Hairyokushoku (Grey-Green)?

Yes, for most jobs. Very close match (ΔE 4). USAAF Light Gray is a little lighter than IJA #1 Hairyokushoku (Grey-Green).

Can I use IJA #1 Hairyokushoku (Grey-Green) instead of USAAF Light Gray?

The same difference applies the other way round: IJA #1 Hairyokushoku (Grey-Green) is a little darker.

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.