Ultramarine Blue vs Abyssal Turquoise

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Abyssal Turquoise is more muted, cooler than Ultramarine Blue.

Can I use Abyssal Turquoise instead of Ultramarine Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Abyssal Turquoise is more muted, cooler than Ultramarine Blue.

Can I use Ultramarine Blue instead of Abyssal Turquoise?

The same difference applies the other way round: Ultramarine Blue 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.