ΔE 13.4, fair: the same colour family, but not a straight swap. Royal Blue is a little darker, warmer than Ultramarine Highlight.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Royal Blue is a little darker, warmer than Ultramarine Highlight.
The same difference applies the other way round: Ultramarine Highlight is a little lighter, 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.
See Ultramarine Highlight on the colour wheel See Royal Blue on the colour wheel
All matches: Ultramarine Highlight equivalents · Royal Blue equivalents