Consul Blue vs Ultramarine Highlight

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Ultramarine Highlight is a little darker, more saturated than Consul Blue.

Can I use Ultramarine Highlight instead of Consul Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Ultramarine Highlight is a little darker, more saturated than Consul Blue.

Can I use Consul Blue instead of Ultramarine Highlight?

The same difference applies the other way round: Consul Blue is a little lighter, 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.