Regal Blue vs Blue Gorkshroom

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Blue Gorkshroom is a little darker, warmer than Regal Blue.

Can I use Blue Gorkshroom instead of Regal Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Blue Gorkshroom is a little darker, warmer than Regal Blue.

Can I use Regal Blue instead of Blue Gorkshroom?

The same difference applies the other way round: Regal Blue is a little lighter, 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.