ΔE 19.2, loose: different enough that you should pick on purpose. Bright Neutral Grey is a little darker, much more muted than Mutant Hue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Bright Neutral Grey is a little darker, much more muted than Mutant Hue.
The same difference applies the other way round: Mutant Hue is a little lighter, much 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.
See Mutant Hue on the colour wheel See Bright Neutral Grey on the colour wheel
All matches: Mutant Hue equivalents · Bright Neutral Grey equivalents