ΔE 16.8, loose: different enough that you should pick on purpose. RLM 78 Light Blue is a little darker, more muted, cooler than Etherium Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). RLM 78 Light Blue is a little darker, more muted, cooler than Etherium Blue.
The same difference applies the other way round: Etherium Blue is a little lighter, more saturated, warmer.
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 Etherium Blue on the colour wheel See RLM 78 Light Blue on the colour wheel
All matches: Etherium Blue equivalents · RLM 78 Light Blue equivalents