Wrack White vs Nuclear White

How close are they?

ΔE 9.2, close: similar, with a visible difference side by side. Nuclear White is a little lighter, more muted than Wrack White.

Can I use Nuclear White instead of Wrack White?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Nuclear White is a little lighter, more muted than Wrack White.

Can I use Wrack White instead of Nuclear White?

The same difference applies the other way round: Wrack White is a little darker, 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.