ΔE 17.3, loose: different enough that you should pick on purpose. Off-White is noticeably lighter, more saturated than Sky Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Off-White is noticeably lighter, more saturated than Sky Grey.
The same difference applies the other way round: Sky Grey is noticeably darker, more muted.
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 Sky Grey on the colour wheel See Off-White on the colour wheel
All matches: Sky Grey equivalents · Off-White equivalents