Stone Grey vs Hammerfall Khaki

How close are they?

ΔE 17.5, loose: different enough that you should pick on purpose. Hammerfall Khaki is much more saturated, cooler than Stone Grey.

Can I use Hammerfall Khaki instead of Stone Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Hammerfall Khaki is much more saturated, cooler than Stone Grey.

Can I use Stone Grey instead of Hammerfall Khaki?

The same difference applies the other way round: Stone Grey is much more muted, 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.