Deep Grey vs Signal Blue

How close are they?

ΔE 8.1, close: similar, with a visible difference side by side. Signal Blue is more muted, cooler than Deep Grey.

Can I use Signal Blue instead of Deep Grey?

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

Can I use Deep Grey instead of Signal Blue?

The same difference applies the other way round: Deep Grey 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.