Old Red vs Forbidden Fruit

How close are they?

ΔE 9.5, close: similar, with a visible difference side by side. Forbidden Fruit is more muted, cooler than Old Red.

Can I use Forbidden Fruit instead of Old Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Forbidden Fruit is more muted, cooler than Old Red.

Can I use Old Red instead of Forbidden Fruit?

The same difference applies the other way round: Old Red is more saturated, warmer.

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.