Isoindolinone Yellow vs Gold Yellow

How close are they?

ΔE 15.8, loose: different enough that you should pick on purpose. Gold Yellow is a little darker, more muted than Isoindolinone Yellow.

Can I use Gold Yellow instead of Isoindolinone Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Gold Yellow is a little darker, more muted than Isoindolinone Yellow.

Can I use Isoindolinone Yellow instead of Gold Yellow?

The same difference applies the other way round: Isoindolinone Yellow is a little lighter, 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.