Fluorescent Chartreuse vs Fluorescent Yellow

How close are they?

ΔE 9.8, close: similar, with a visible difference side by side. Fluorescent Yellow is more muted than Fluorescent Chartreuse.

Can I use Fluorescent Yellow instead of Fluorescent Chartreuse?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Fluorescent Yellow is more muted than Fluorescent Chartreuse.

Can I use Fluorescent Chartreuse instead of Fluorescent Yellow?

The same difference applies the other way round: Fluorescent Chartreuse is 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.