AE-9/AII Light Grey vs Insignia White

How close are they?

ΔE 8.4, close: similar, with a visible difference side by side. Insignia White is more saturated than AE-9/AII Light Grey.

Can I use Insignia White instead of AE-9/AII Light Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Insignia White is more saturated than AE-9/AII Light Grey.

Can I use AE-9/AII Light Grey instead of Insignia White?

The same difference applies the other way round: AE-9/AII Light Grey is 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.