Regiment Grey vs IJN Gray (Maizuru Arsenal)

How close are they?

ΔE 9.3, close: similar, with a visible difference side by side. IJN Gray (Maizuru Arsenal) is a little lighter than Regiment Grey.

Can I use IJN Gray (Maizuru Arsenal) instead of Regiment Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). IJN Gray (Maizuru Arsenal) is a little lighter than Regiment Grey.

Can I use Regiment Grey instead of IJN Gray (Maizuru Arsenal)?

The same difference applies the other way round: Regiment Grey 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.