Imperium Blue vs Blue Violet

How close are they?

ΔE 20.7, loose: different enough that you should pick on purpose. Blue Violet is a little lighter, much more muted, warmer than Imperium Blue.

Can I use Blue Violet instead of Imperium Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Blue Violet is a little lighter, much more muted, warmer than Imperium Blue.

Can I use Imperium Blue instead of Blue Violet?

The same difference applies the other way round: Imperium Blue is a little darker, much more saturated, 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.