Frost Blue vs Etherium Blue

How close are they?

ΔE 9.8, close: similar, with a visible difference side by side. Etherium Blue is a little darker, more saturated than Frost Blue.

Can I use Etherium Blue instead of Frost Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Etherium Blue is a little darker, more saturated than Frost Blue.

Can I use Frost Blue instead of Etherium Blue?

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