ΔE 18.7, loose: different enough that you should pick on purpose. Gehenna's Gold is a little darker, much more saturated, warmer than Old Gold.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Gehenna's Gold is a little darker, much more saturated, warmer than Old Gold.
The same difference applies the other way round: Old Gold is a little lighter, much more muted, 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.
See Old Gold on the colour wheel See Gehenna's Gold on the colour wheel
All matches: Old Gold equivalents · Gehenna's Gold equivalents