Granite Grey vs USA Flat Brown

How close are they?

ΔE 16.0, loose: different enough that you should pick on purpose. USA Flat Brown is a little darker, much more saturated than Granite Grey.

Can I use USA Flat Brown instead of Granite Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). USA Flat Brown is a little darker, much more saturated than Granite Grey.

Can I use Granite Grey instead of USA Flat Brown?

The same difference applies the other way round: Granite Grey 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.