ΔE 19.7, loose: different enough that you should pick on purpose. Mead Violet is a little darker, more saturated, warmer than Fog Grey.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Mead Violet is a little darker, more saturated, warmer than Fog Grey.
The same difference applies the other way round: Fog Grey is a little lighter, more muted, cooler.
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 Fog Grey on the colour wheel See Mead Violet on the colour wheel
All matches: Fog Grey equivalents · Mead Violet equivalents