Tyran Blue vs Vicious Purple

How close are they?

ΔE 30.0, loose: different enough that you should pick on purpose. Vicious Purple is a little darker, warmer than Tyran Blue.

Can I use Vicious Purple instead of Tyran Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Vicious Purple is a little darker, warmer than Tyran Blue.

Can I use Tyran Blue instead of Vicious Purple?

The same difference applies the other way round: Tyran Blue 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.