Thunderhawk Blue vs Blue Mountain

How close are they?

ΔE 9.2, close: similar, with a visible difference side by side. Blue Mountain is a little lighter, warmer than Thunderhawk Blue.

Can I use Blue Mountain instead of Thunderhawk Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Blue Mountain is a little lighter, warmer than Thunderhawk Blue.

Can I use Thunderhawk Blue instead of Blue Mountain?

The same difference applies the other way round: Thunderhawk Blue is a little darker, 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.