ΔE 14.9, fair: the same colour family, but not a straight swap. Saffron Sunset is a little lighter, cooler than Fire Giant Orange. They are different kinds of paint: Army Painter Fire Giant Orange is a one-coat contrast-style paint and Reaper Saffron Sunset is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Saffron Sunset is a little lighter, cooler than Fire Giant Orange. They are different kinds of paint.
The same difference applies the other way round: Fire Giant Orange is a little darker, 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.
See Fire Giant Orange on the colour wheel See Saffron Sunset on the colour wheel
All matches: Fire Giant Orange equivalents · Saffron Sunset equivalents