Blue Base vs Imperial Blue

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Imperial Blue is more saturated than Blue Base.

Can I use Imperial Blue instead of Blue Base?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Imperial Blue is more saturated than Blue Base.

Can I use Blue Base instead of Imperial Blue?

The same difference applies the other way round: Blue Base 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.