Etherium Blue vs Spirit Blue

How close are they?

ΔE 22.8, loose: different enough that you should pick on purpose. Spirit Blue is a little darker, more saturated than Etherium Blue.

Can I use Spirit Blue instead of Etherium Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Spirit Blue is a little darker, more saturated than Etherium Blue.

Can I use Etherium Blue instead of Spirit Blue?

The same difference applies the other way round: Etherium 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.