Forbidden Fruit vs Titan Mars Pale

How close are they?

ΔE 33.3, loose: different enough that you should pick on purpose. Titan Mars Pale is noticeably lighter, more muted, warmer than Forbidden Fruit.

Can I use Titan Mars Pale instead of Forbidden Fruit?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 33). Titan Mars Pale is noticeably lighter, more muted, warmer than Forbidden Fruit.

Can I use Forbidden Fruit instead of Titan Mars Pale?

The same difference applies the other way round: Forbidden Fruit is noticeably darker, more saturated, 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.