El Dorado vs Forged Red

How close are they?

ΔE 26.1, loose: different enough that you should pick on purpose. Forged Red is a little darker, warmer than El Dorado.

Can I use Forged Red instead of El Dorado?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Forged Red is a little darker, warmer than El Dorado.

Can I use El Dorado instead of Forged Red?

The same difference applies the other way round: El Dorado is a little lighter, cooler.

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.