Violent Vermillion vs Inferno Orange

How close are they?

ΔE 24.3, loose: different enough that you should pick on purpose. Inferno Orange is a little darker, much more saturated than Violent Vermillion.

Can I use Inferno Orange instead of Violent Vermillion?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Inferno Orange is a little darker, much more saturated than Violent Vermillion.

Can I use Violent Vermillion instead of Inferno Orange?

The same difference applies the other way round: Violent Vermillion is a little lighter, much 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.