ΔE 51.1, loose: different enough that you should pick on purpose. Space Grey is noticeably darker, cooler than Pastel Seafoam.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 51). Space Grey is noticeably darker, cooler than Pastel Seafoam.
The same difference applies the other way round: Pastel Seafoam is noticeably lighter, 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 Pastel Seafoam on the colour wheel See Space Grey on the colour wheel
All matches: Pastel Seafoam equivalents · Space Grey equivalents