Safety Orange vs NOVA Orange

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. NOVA Orange is a little darker, much more saturated than Safety Orange.

Can I use NOVA Orange instead of Safety Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). NOVA Orange is a little darker, much more saturated than Safety Orange.

Can I use Safety Orange instead of NOVA Orange?

The same difference applies the other way round: Safety Orange 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.