ΔE 15.8, loose: different enough that you should pick on purpose. Pure Orange is a little darker, warmer than Imperial Fist. They are different kinds of paint: Citadel Imperial Fist is a one-coat contrast-style paint and Tamiya Pure Orange is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Pure Orange is a little darker, warmer than Imperial Fist. They are different kinds of paint.
The same difference applies the other way round: Imperial Fist is a little lighter, cooler.
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.
See Imperial Fist on the colour wheel See Pure Orange on the colour wheel
All matches: Imperial Fist equivalents · Pure Orange equivalents