Ultramarine Shadow vs Signal Blue

How close are they?

ΔE 9.0, close: similar, with a visible difference side by side. Signal Blue is more muted, warmer than Ultramarine Shadow.

Can I use Signal Blue instead of Ultramarine Shadow?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Signal Blue is more muted, warmer than Ultramarine Shadow.

Can I use Ultramarine Shadow instead of Signal Blue?

The same difference applies the other way round: Ultramarine Shadow is more saturated, cooler.

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.