ΔE 18.6, loose: different enough that you should pick on purpose. Fluorescent Orange is a little lighter, much more saturated than Evil Sunz Scarlet. They are different kinds of paint: Citadel Evil Sunz Scarlet is an opaque base/layer paint and Mr. Hobby Fluorescent Orange is a fluorescent or effect 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 19). Fluorescent Orange is a little lighter, much more saturated than Evil Sunz Scarlet. They are different kinds of paint.
The same difference applies the other way round: Evil Sunz Scarlet is a little darker, much more muted.
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 Evil Sunz Scarlet on the colour wheel See Fluorescent Orange on the colour wheel
All matches: Evil Sunz Scarlet equivalents · Fluorescent Orange equivalents