ΔE 16.3, loose: different enough that you should pick on purpose. Middle Stone is a little darker, more muted, cooler than T'au Light Ochre.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Middle Stone is a little darker, more muted, cooler than T'au Light Ochre.
The same difference applies the other way round: T'au Light Ochre is a little lighter, more saturated, warmer.
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 T'au Light Ochre on the colour wheel See Middle Stone on the colour wheel
All matches: T'au Light Ochre equivalents · Middle Stone equivalents