Dark DAK Sand vs Green Beret

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Green Beret is a little darker, more muted, cooler than Dark DAK Sand.

Can I use Green Beret instead of Dark DAK Sand?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Green Beret is a little darker, more muted, cooler than Dark DAK Sand.

Can I use Dark DAK Sand instead of Green Beret?

The same difference applies the other way round: Dark DAK Sand is a little lighter, more saturated, 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.