Karak Stone vs Raw Sienna

How close are they?

ΔE 23.9, loose: different enough that you should pick on purpose. Raw Sienna is a little darker, much more saturated, warmer than Karak Stone.

Can I use Raw Sienna instead of Karak Stone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Raw Sienna is a little darker, much more saturated, warmer than Karak Stone.

Can I use Karak Stone instead of Raw Sienna?

The same difference applies the other way round: Karak Stone is a little lighter, much more muted, cooler.

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.