Thunderous Blue vs Dark Blue RLM24

How close are they?

ΔE 8.0, close: similar, with a visible difference side by side. Dark Blue RLM24 is a little darker, more muted than Thunderous Blue.

Can I use Dark Blue RLM24 instead of Thunderous Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Dark Blue RLM24 is a little darker, more muted than Thunderous Blue.

Can I use Thunderous Blue instead of Dark Blue RLM24?

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

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.