Ultramarines Blue vs Paralyze Blue

How close are they?

ΔE 30.0, loose: different enough that you should pick on purpose. Paralyze Blue is noticeably lighter, more muted, cooler than Ultramarines Blue.

Can I use Paralyze Blue instead of Ultramarines Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Paralyze Blue is noticeably lighter, more muted, cooler than Ultramarines Blue.

Can I use Ultramarines Blue instead of Paralyze Blue?

The same difference applies the other way round: Ultramarines Blue is noticeably darker, more saturated, warmer.

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.