ΔE 9.7, close: similar, with a visible difference side by side. T'au Light Ochre is warmer than Mustard Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). T'au Light Ochre is warmer than Mustard Yellow.
The same difference applies the other way round: Mustard Yellow is 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 T'au Light Ochre on the colour wheel
All matches: Mustard Yellow equivalents · T'au Light Ochre equivalents