ΔE 11.6, fair: the same colour family, but not a straight swap. Yellow Ink is a little lighter than Vivid Volt. They are different kinds of paint: Army Painter Vivid Volt is an opaque base/layer paint and Formula P3 Yellow Ink is an ink, glaze or transparent 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). Yellow Ink is a little lighter than Vivid Volt. They are different kinds of paint.
The same difference applies the other way round: Vivid Volt is a little darker.
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 Vivid Volt on the colour wheel See Yellow Ink on the colour wheel
All matches: Vivid Volt equivalents · Yellow Ink equivalents