Sapphire Gem vs Ultramarine

How close are they?

ΔE 16.7, loose: different enough that you should pick on purpose. Ultramarine is a little darker, more saturated, warmer than Sapphire Gem.

Can I use Ultramarine instead of Sapphire Gem?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Ultramarine is a little darker, more saturated, warmer than Sapphire Gem.

Can I use Sapphire Gem instead of Ultramarine?

The same difference applies the other way round: Sapphire Gem is a little lighter, more muted, cooler.

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.