Blue-Green vs Wizards Orb

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Wizards Orb is a little darker, more saturated than Blue-Green.

Can I use Wizards Orb instead of Blue-Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Wizards Orb is a little darker, more saturated than Blue-Green.

Can I use Blue-Green instead of Wizards Orb?

The same difference applies the other way round: Blue-Green 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.