Karak Stone vs Ambush Yellow

How close are they?

ΔE 19.8, loose: different enough that you should pick on purpose. Ambush Yellow is noticeably lighter, more saturated, cooler than Karak Stone.

Can I use Ambush Yellow instead of Karak Stone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Ambush Yellow is noticeably lighter, more saturated, cooler than Karak Stone.

Can I use Karak Stone instead of Ambush Yellow?

The same difference applies the other way round: Karak Stone is noticeably darker, 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.