Evil Sunz Scarlet vs Fire Flame

How close are they?

ΔE 17.7, loose: different enough that you should pick on purpose. Fire Flame is noticeably lighter, much more saturated than Evil Sunz Scarlet.

Can I use Fire Flame instead of Evil Sunz Scarlet?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Fire Flame is noticeably lighter, much more saturated than Evil Sunz Scarlet.

Can I use Evil Sunz Scarlet instead of Fire Flame?

The same difference applies the other way round: Evil Sunz Scarlet is noticeably 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.