Dark Warm Flesh vs US Interior Yellow

How close are they?

ΔE 17.7, loose: different enough that you should pick on purpose. US Interior Yellow is noticeably darker, cooler than Dark Warm Flesh.

Can I use US Interior Yellow instead of Dark Warm Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). US Interior Yellow is noticeably darker, cooler than Dark Warm Flesh.

Can I use Dark Warm Flesh instead of US Interior Yellow?

The same difference applies the other way round: Dark Warm Flesh is noticeably lighter, 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.