ΔE 12.7, fair: the same colour family, but not a straight swap. RLM 79 Sand Yellow is noticeably darker than Karak Stone.
Can I use RLM 79 Sand Yellow instead of Karak Stone?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). RLM 79 Sand Yellow is noticeably darker than Karak Stone.
Can I use Karak Stone instead of RLM 79 Sand Yellow?
The same difference applies the other way round: Karak Stone is noticeably lighter.
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.