Occultist Cloak vs Grey Mist

How close are they?

ΔE 16.7, loose: different enough that you should pick on purpose. Grey Mist is noticeably lighter, more muted than Occultist Cloak.

Can I use Grey Mist instead of Occultist Cloak?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Grey Mist is noticeably lighter, more muted than Occultist Cloak.

Can I use Occultist Cloak instead of Grey Mist?

The same difference applies the other way round: Occultist Cloak is noticeably 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.