Melancholic Grey vs Blue Horror

How close are they?

ΔE 9.6, close: similar, with a visible difference side by side. Blue Horror is a little darker, more saturated than Melancholic Grey.

Can I use Blue Horror instead of Melancholic Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Blue Horror is a little darker, more saturated than Melancholic Grey.

Can I use Melancholic Grey instead of Blue Horror?

The same difference applies the other way round: Melancholic Grey is a little lighter, more muted.

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.