Thunderous Blue vs Abyssal Turquoise

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Abyssal Turquoise is a little darker, more muted, cooler than Thunderous Blue.

Can I use Abyssal Turquoise instead of Thunderous Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Abyssal Turquoise is a little darker, more muted, cooler than Thunderous Blue.

Can I use Thunderous Blue instead of Abyssal Turquoise?

The same difference applies the other way round: Thunderous Blue is a little lighter, 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.