Fahrenheit vs Forged Red

How close are they?

ΔE 20.9, loose: different enough that you should pick on purpose. Forged Red is a little lighter, much more muted than Fahrenheit.

Can I use Forged Red instead of Fahrenheit?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Forged Red is a little lighter, much more muted than Fahrenheit.

Can I use Fahrenheit instead of Forged Red?

The same difference applies the other way round: Fahrenheit is a little darker, much more saturated.

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.