Terrestrial Titan vs Phthalo Cyanine Blue

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Phthalo Cyanine Blue is a little lighter, more saturated, cooler than Terrestrial Titan.

Can I use Phthalo Cyanine Blue instead of Terrestrial Titan?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Phthalo Cyanine Blue is a little lighter, more saturated, cooler than Terrestrial Titan.

Can I use Terrestrial Titan instead of Phthalo Cyanine Blue?

The same difference applies the other way round: Terrestrial Titan is a little darker, more muted, 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.