Sotek Green vs Phthalo Turquoise Light

How close are they?

ΔE 17.6, loose: different enough that you should pick on purpose. Phthalo Turquoise Light is more muted, cooler than Sotek Green.

Can I use Phthalo Turquoise Light instead of Sotek Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Phthalo Turquoise Light is more muted, cooler than Sotek Green.

Can I use Sotek Green instead of Phthalo Turquoise Light?

The same difference applies the other way round: Sotek Green is more saturated, 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.