Nazdreg Yellow vs Radiant Orange

How close are they?

ΔE 46.7, loose: different enough that you should pick on purpose. Radiant Orange is noticeably darker, much more muted, warmer than Nazdreg Yellow.

Can I use Radiant Orange instead of Nazdreg Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 47). Radiant Orange is noticeably darker, much more muted, warmer than Nazdreg Yellow.

Can I use Nazdreg Yellow instead of Radiant Orange?

The same difference applies the other way round: Nazdreg Yellow is noticeably lighter, 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.