Shiny Gold vs Radiant Yellow

How close are they?

ΔE 18.4, loose: different enough that you should pick on purpose. Radiant Yellow is a little lighter, much more muted, cooler than Shiny Gold.

Can I use Radiant Yellow instead of Shiny Gold?

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

Can I use Shiny Gold instead of Radiant Yellow?

The same difference applies the other way round: Shiny Gold is a little darker, much more saturated, 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.