Rock Grey vs Krieg Khaki

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Krieg Khaki is a little darker, more saturated than Rock Grey.

Can I use Krieg Khaki instead of Rock Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Krieg Khaki is a little darker, more saturated than Rock Grey.

Can I use Rock Grey instead of Krieg Khaki?

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