ΔE 16.3, loose: different enough that you should pick on purpose. Old Gold is noticeably darker, more saturated than Iron Warriors.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Old Gold is noticeably darker, more saturated than Iron Warriors.
The same difference applies the other way round: Iron Warriors is noticeably lighter, more muted.
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 Iron Warriors on the colour wheel See Old Gold on the colour wheel
All matches: Iron Warriors equivalents · Old Gold equivalents