ΔE 13.2, fair: the same colour family, but not a straight swap. Phthalo Turquoise Light is a little darker, more saturated, cooler than Fog Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Phthalo Turquoise Light is a little darker, more saturated, cooler than Fog Grey.
The same difference applies the other way round: Fog Grey is a little lighter, more muted, warmer.
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 Phthalo Turquoise Light on the colour wheel
All matches: Fog Grey equivalents · Phthalo Turquoise Light equivalents