Naples Yellow Deep vs Yellow Ochre

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Yellow Ochre is a little darker, much more muted than Naples Yellow Deep.

Can I use Yellow Ochre instead of Naples Yellow Deep?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Yellow Ochre is a little darker, much more muted than Naples Yellow Deep.

Can I use Naples Yellow Deep instead of Yellow Ochre?

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