ΔE 9.5, close: similar, with a visible difference side by side. Fluor Yellow is a little lighter than Poisonous Cloud. They are different kinds of paint: Army Painter Poisonous Cloud is an opaque base/layer paint and Green Stuff World Fluor Yellow is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Fluor Yellow is a little lighter than Poisonous Cloud. They are different kinds of paint.
The same difference applies the other way round: Poisonous Cloud 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 Poisonous Cloud on the colour wheel See Fluor Yellow on the colour wheel
All matches: Poisonous Cloud equivalents · Fluor Yellow equivalents