Frostbite vs Glacier Blue

How close are they?

ΔE 7.2, close: similar, with a visible difference side by side. Glacier Blue is a little darker, more saturated than Frostbite.

Can I use Glacier Blue instead of Frostbite?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Glacier Blue is a little darker, more saturated than Frostbite.

Can I use Frostbite instead of Glacier Blue?

The same difference applies the other way round: Frostbite is a little lighter, 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.