Terrestrial Titan vs Huldra Blue

How close are they?

ΔE 6.8, close: similar, with a visible difference side by side. Huldra Blue is more muted, cooler than Terrestrial Titan.

Can I use Huldra Blue instead of Terrestrial Titan?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Huldra Blue is more muted, cooler than Terrestrial Titan.

Can I use Terrestrial Titan instead of Huldra Blue?

The same difference applies the other way round: Terrestrial Titan 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.