Screaming Sun vs Toxic Yellow

How close are they?

ΔE 34.9, loose: different enough that you should pick on purpose. Toxic Yellow is a little darker, much more muted than Screaming Sun.

Can I use Toxic Yellow instead of Screaming Sun?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 35). Toxic Yellow is a little darker, much more muted than Screaming Sun.

Can I use Screaming Sun instead of Toxic Yellow?

The same difference applies the other way round: Screaming Sun is a little lighter, much 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.