Hellspawn Red vs Fire Flame

How close are they?

ΔE 23.1, loose: different enough that you should pick on purpose. Fire Flame is a little lighter, much more saturated than Hellspawn Red.

Can I use Fire Flame instead of Hellspawn Red?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Fire Flame is a little lighter, much more saturated than Hellspawn Red.

Can I use Hellspawn Red instead of Fire Flame?

The same difference applies the other way round: Hellspawn Red 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.