Viking Gold vs Radiant Yellow

How close are they?

ΔE 17.6, loose: different enough that you should pick on purpose. Radiant Yellow is a little lighter, more saturated, cooler than Viking Gold.

Can I use Radiant Yellow instead of Viking Gold?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Radiant Yellow is a little lighter, more saturated, cooler than Viking Gold.

Can I use Viking Gold instead of Radiant Yellow?

The same difference applies the other way round: Viking Gold is a little darker, more muted, warmer.

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.