ΔE 11.8, fair: the same colour family, but not a straight swap. Bad Moon Yellow is a little darker, more saturated than Matt Yellow. They are different kinds of paint: AMMO by Mig Matt Yellow is an ink, glaze or transparent paint and Citadel Bad Moon Yellow is a one-coat contrast-style 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 12). Bad Moon Yellow is a little darker, more saturated than Matt Yellow. They are different kinds of paint.
The same difference applies the other way round: Matt Yellow is a little lighter, more muted.
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 Yellow on the colour wheel See Bad Moon Yellow on the colour wheel
All matches: Matt Yellow equivalents · Bad Moon Yellow equivalents