ΔE 13.4, fair: the same colour family, but not a straight swap. Green Sky is a little lighter, more muted than Ethereal Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Green Sky is a little lighter, more muted than Ethereal Green.
The same difference applies the other way round: Ethereal Green is a little darker, more saturated.
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 Ethereal Green on the colour wheel See Green Sky on the colour wheel
All matches: Ethereal Green equivalents · Green Sky equivalents