Light DAK Sand vs Yellow Ochre

How close are they?

ΔE 18.9, loose: different enough that you should pick on purpose. Yellow Ochre is a little darker, much more saturated than Light DAK Sand.

Can I use Yellow Ochre instead of Light DAK Sand?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Yellow Ochre is a little darker, much more saturated than Light DAK Sand.

Can I use Light DAK Sand instead of Yellow Ochre?

The same difference applies the other way round: Light DAK Sand is a little lighter, much 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.