Glittering Loot vs Radiant Yellow

How close are they?

ΔE 16.4, loose: different enough that you should pick on purpose. Radiant Yellow is noticeably darker, much more muted than Glittering Loot.

Can I use Radiant Yellow instead of Glittering Loot?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Radiant Yellow is noticeably darker, much more muted than Glittering Loot.

Can I use Glittering Loot instead of Radiant Yellow?

The same difference applies the other way round: Glittering Loot 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.