ΔE 10.9, fair: the same colour family, but not a straight swap. Elf Skin Tone is a little lighter, more muted than Mars Yellow.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Elf Skin Tone is a little lighter, more muted than Mars Yellow.
The same difference applies the other way round: Mars Yellow is a little darker, 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 Mars Yellow on the colour wheel See Elf Skin Tone on the colour wheel
All matches: Mars Yellow equivalents · Elf Skin Tone equivalents