Mithril vs Omega Blue

How close are they?

ΔE 29.1, loose: different enough that you should pick on purpose. Omega Blue is a little darker, much more saturated than Mithril.

Can I use Omega Blue instead of Mithril?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Omega Blue is a little darker, much more saturated than Mithril.

Can I use Mithril instead of Omega Blue?

The same difference applies the other way round: Mithril is a little lighter, much 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.