ΔE 9.8, close: similar, with a visible difference side by side. Sentient Turquoise is a little darker than Skink Blue.
Can I use Sentient Turquoise instead of Skink Blue?
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Sentient Turquoise is a little darker than Skink Blue.
Can I use Skink Blue instead of Sentient Turquoise?
The same difference applies the other way round: Skink Blue is a little lighter.
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.