Marine Mist vs Sky Blue

How close are they?

ΔE 8.4, close: similar, with a visible difference side by side. Sky Blue is a little lighter, cooler than Marine Mist.

Can I use Sky Blue instead of Marine Mist?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sky Blue is a little lighter, cooler than Marine Mist.

Can I use Marine Mist instead of Sky Blue?

The same difference applies the other way round: Marine Mist is a little darker, 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.