Safety Orange vs Vulcan Orange

How close are they?

ΔE 22.7, loose: different enough that you should pick on purpose. Vulcan Orange is noticeably darker, much more muted than Safety Orange.

Can I use Vulcan Orange instead of Safety Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Vulcan Orange is noticeably darker, much more muted than Safety Orange.

Can I use Safety Orange instead of Vulcan Orange?

The same difference applies the other way round: Safety Orange is noticeably lighter, much more saturated.

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.