Tyrant Skull vs Cloudy Sky

How close are they?

ΔE 7.3, close: similar, with a visible difference side by side. Cloudy Sky is warmer than Tyrant Skull.

Can I use Cloudy Sky instead of Tyrant Skull?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Cloudy Sky is warmer than Tyrant Skull.

Can I use Tyrant Skull instead of Cloudy Sky?

The same difference applies the other way round: Tyrant Skull is 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.