ΔE 11.9, fair: the same colour family, but not a straight swap. Celestial Blue is noticeably darker than Etherium Blue.
Can I use Celestial Blue instead of Etherium Blue?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Celestial Blue is noticeably darker than Etherium Blue.
Can I use Etherium Blue instead of Celestial Blue?
The same difference applies the other way round: Etherium Blue is noticeably lighter.
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.