Toxic Mist vs Spirit Blue

How close are they?

ΔE 8.1, close: similar, with a visible difference side by side. Spirit Blue is a little darker, cooler than Toxic Mist.

Can I use Spirit Blue instead of Toxic Mist?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Spirit Blue is a little darker, cooler than Toxic Mist.

Can I use Toxic Mist instead of Spirit Blue?

The same difference applies the other way round: Toxic Mist 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.