ΔE 15.4, loose: different enough that you should pick on purpose. Royal Blue is more saturated, warmer than Brilliant Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Royal Blue is more saturated, warmer than Brilliant Blue.
The same difference applies the other way round: Brilliant Blue is 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.
See Brilliant Blue on the colour wheel See Royal Blue on the colour wheel
All matches: Brilliant Blue equivalents · Royal Blue equivalents