Hot Pink vs Medium Magenta

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Medium Magenta is a little darker, cooler than Hot Pink.

Can I use Medium Magenta instead of Hot Pink?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Medium Magenta is a little darker, cooler than Hot Pink.

Can I use Hot Pink instead of Medium Magenta?

The same difference applies the other way round: Hot Pink is a little lighter, warmer.

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.