ΔE 14.9, fair: the same colour family, but not a straight swap. Dark Sun Yellow is noticeably darker, cooler than Peachy Flesh. They are different kinds of paint: Army Painter Peachy Flesh is a one-coat contrast-style paint and Two Thin Coats Dark Sun Yellow 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 15). Dark Sun Yellow is noticeably darker, cooler than Peachy Flesh. They are different kinds of paint.
The same difference applies the other way round: Peachy Flesh is noticeably lighter, 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 Peachy Flesh on the colour wheel See Dark Sun Yellow on the colour wheel
All matches: Peachy Flesh equivalents · Dark Sun Yellow equivalents