ΔE 20.7, loose: different enough that you should pick on purpose. Fire Orange is a little darker, cooler than Gryph-Hound Orange. They are different kinds of paint: Citadel Gryph-Hound Orange is a one-coat contrast-style paint and Reaper Fire 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 21). Fire Orange is a little darker, cooler than Gryph-Hound Orange. They are different kinds of paint.
The same difference applies the other way round: Gryph-Hound Orange 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.
See Gryph-Hound Orange on the colour wheel See Fire Orange on the colour wheel
All matches: Gryph-Hound Orange equivalents · Fire Orange equivalents