ΔE 10.9, fair: the same colour family, but not a straight swap. Desert Skin is noticeably darker than Matt Dwarf Flesh. They are different kinds of paint: AMMO by Mig Matt Dwarf Flesh is an ink, glaze or transparent paint and Army Painter Desert Skin 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 11). Desert Skin is noticeably darker than Matt Dwarf Flesh. They are different kinds of paint.
The same difference applies the other way round: Matt Dwarf Flesh is noticeably lighter.
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 Matt Dwarf Flesh on the colour wheel See Desert Skin on the colour wheel
All matches: Matt Dwarf Flesh equivalents · Desert Skin equivalents