ΔE 17.7, loose: different enough that you should pick on purpose. Etherium Blue is a little lighter, more muted, warmer than Aegis Aqua.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Etherium Blue is a little lighter, more muted, warmer than Aegis Aqua.
The same difference applies the other way round: Aegis Aqua is a little darker, more saturated, cooler.
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.
See Aegis Aqua on the colour wheel See Etherium Blue on the colour wheel
All matches: Aegis Aqua equivalents · Etherium Blue equivalents