Poisonous Cloud vs Lemon Yellow

How close are they?

ΔE 8.6, close: similar, with a visible difference side by side. Lemon Yellow is more saturated than Poisonous Cloud.

Can I use Lemon Yellow instead of Poisonous Cloud?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Lemon Yellow is more saturated than Poisonous Cloud.

Can I use Poisonous Cloud instead of Lemon Yellow?

The same difference applies the other way round: Poisonous Cloud is 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.