Bright Ivory vs Insignia White

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Insignia White is a little darker, cooler than Bright Ivory.

Can I use Insignia White instead of Bright Ivory?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Insignia White is a little darker, cooler than Bright Ivory.

Can I use Bright Ivory instead of Insignia White?

The same difference applies the other way round: Bright Ivory is a little lighter, warmer.

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.