Macragge Blue vs Deep Blue

How close are they?

ΔE 16.4, loose: different enough that you should pick on purpose. Deep Blue is a little darker, much more muted than Macragge Blue.

Can I use Deep Blue instead of Macragge Blue?

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

Can I use Macragge Blue instead of Deep Blue?

The same difference applies the other way round: Macragge Blue is a little lighter, much more saturated.

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.