Drab Green vs Green Beret

How close are they?

ΔE 18.9, loose: different enough that you should pick on purpose. Green Beret is a little darker, much more muted, warmer than Drab Green.

Can I use Green Beret instead of Drab Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Green Beret is a little darker, much more muted, warmer than Drab Green.

Can I use Drab Green instead of Green Beret?

The same difference applies the other way round: Drab Green is a little lighter, much more saturated, cooler.

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.