ΔE 17.2, loose: different enough that you should pick on purpose. Pale Brown is noticeably darker, much more saturated than Moonstone Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Pale Brown is noticeably darker, much more saturated than Moonstone Grey.
The same difference applies the other way round: Moonstone Grey is noticeably lighter, much 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 Moonstone Grey on the colour wheel See Pale Brown on the colour wheel
All matches: Moonstone Grey equivalents · Pale Brown equivalents