Consul Blue vs Mediterranean Blue

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Mediterranean Blue is a little darker, much more saturated than Consul Blue.

Can I use Mediterranean Blue instead of Consul Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Mediterranean Blue is a little darker, much more saturated than Consul Blue.

Can I use Consul Blue instead of Mediterranean Blue?

The same difference applies the other way round: Consul Blue 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.