ΔE 12.1, fair: the same colour family, but not a straight swap. Bismuth Yellow is a little darker, more muted than Flash Gitz Yellow.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Bismuth Yellow is a little darker, more muted than Flash Gitz Yellow.
The same difference applies the other way round: Flash Gitz Yellow is a little lighter, 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 Flash Gitz Yellow on the colour wheel See Bismuth Yellow on the colour wheel
All matches: Flash Gitz Yellow equivalents · Bismuth Yellow equivalents