Pink Potion vs Stonewall Grey

How close are they?

ΔE 23.5, loose: different enough that you should pick on purpose. Stonewall Grey is a little darker, much more muted than Pink Potion.

Can I use Stonewall Grey instead of Pink Potion?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Stonewall Grey is a little darker, much more muted than Pink Potion.

Can I use Pink Potion instead of Stonewall Grey?

The same difference applies the other way round: Pink Potion 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.