ΔE 14.9, fair: the same colour family, but not a straight swap. Tallarn Sand is a little darker, more muted, warmer than Mustard Yellow.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Tallarn Sand is a little darker, more muted, warmer than Mustard Yellow.
The same difference applies the other way round: Mustard Yellow is a little lighter, more saturated, 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.
See Mustard Yellow on the colour wheel See Tallarn Sand on the colour wheel
All matches: Mustard Yellow equivalents · Tallarn Sand equivalents