Pale Grey (RLM 76) vs Leviathan Light

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Leviathan Light is a little lighter than Pale Grey (RLM 76).

Can I use Leviathan Light instead of Pale Grey (RLM 76)?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Leviathan Light is a little lighter than Pale Grey (RLM 76).

Can I use Pale Grey (RLM 76) instead of Leviathan Light?

The same difference applies the other way round: Pale Grey (RLM 76) is a little darker.

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.