ΔE 10.4, fair: the same colour family, but not a straight swap. T'au Light Ochre is a little darker, more muted than Orange. They are different kinds of paint: AMMO by Mig Orange is an ink, glaze or transparent paint and Citadel T'au Light Ochre is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). T'au Light Ochre is a little darker, more muted than Orange. They are different kinds of paint.
The same difference applies the other way round: Orange is a little lighter, more saturated.
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 Orange on the colour wheel See T'au Light Ochre on the colour wheel
All matches: Orange equivalents · T'au Light Ochre equivalents