ΔE 15.1, loose: different enough that you should pick on purpose. Space Wolves Grey is noticeably darker, more muted, cooler than Pastel Indigo.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Space Wolves Grey is noticeably darker, more muted, cooler than Pastel Indigo.
The same difference applies the other way round: Pastel Indigo is noticeably 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 Pastel Indigo on the colour wheel See Space Wolves Grey on the colour wheel
All matches: Pastel Indigo equivalents · Space Wolves Grey equivalents