Vivid Pink vs Witch Purple

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Witch Purple is a little darker than Vivid Pink.

Can I use Witch Purple instead of Vivid Pink?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Witch Purple is a little darker than Vivid Pink.

Can I use Vivid Pink instead of Witch Purple?

The same difference applies the other way round: Vivid Pink is a little lighter.

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.