IJN Gray Green Nakajima vs Light Blue RLM76

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Light Blue RLM76 is a little lighter, more muted than IJN Gray Green Nakajima.

Can I use Light Blue RLM76 instead of IJN Gray Green Nakajima?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Light Blue RLM76 is a little lighter, more muted than IJN Gray Green Nakajima.

Can I use IJN Gray Green Nakajima instead of Light Blue RLM76?

The same difference applies the other way round: IJN Gray Green Nakajima is a little darker, more saturated.

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.