Dawnstone vs Ground Brown

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Ground Brown is a little darker, more saturated than Dawnstone.

Can I use Ground Brown instead of Dawnstone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Ground Brown is a little darker, more saturated than Dawnstone.

Can I use Dawnstone instead of Ground Brown?

The same difference applies the other way round: Dawnstone is a little lighter, 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.