ΔE 17.6, loose: different enough that you should pick on purpose. Flat Green is a little lighter, much more saturated than Dawnstone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Flat Green is a little lighter, much more saturated than Dawnstone.
The same difference applies the other way round: Dawnstone is a little darker, 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.
See Dawnstone on the colour wheel See Flat Green on the colour wheel
All matches: Dawnstone equivalents · Flat Green equivalents