Dark Yellow 2 vs Green Ochre

How close are they?

ΔE 17.8, loose: different enough that you should pick on purpose. Green Ochre is noticeably darker, more muted than Dark Yellow 2.

Can I use Green Ochre instead of Dark Yellow 2?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Green Ochre is noticeably darker, more muted than Dark Yellow 2.

Can I use Dark Yellow 2 instead of Green Ochre?

The same difference applies the other way round: Dark Yellow 2 is noticeably 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.