ΔE 10.8, fair: the same colour family, but not a straight swap. Sky Grey is a little darker, more muted than Donkey Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Sky Grey is a little darker, more muted than Donkey Grey.
The same difference applies the other way round: Donkey Grey is a little lighter, 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 Donkey Grey on the colour wheel See Sky Grey on the colour wheel
All matches: Donkey Grey equivalents · Sky Grey equivalents