ΔE 11.0, fair: the same colour family, but not a straight swap. Sand Yellow RLM79 is noticeably lighter than Shield Brown.
Can I use Sand Yellow RLM79 instead of Shield Brown?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Sand Yellow RLM79 is noticeably lighter than Shield Brown.
Can I use Shield Brown instead of Sand Yellow RLM79?
The same difference applies the other way round: Shield Brown is noticeably darker.
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.