Trollslayer Orange vs Fire Orange

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. Fire Orange is more muted than Trollslayer Orange.

Can I use Fire Orange instead of Trollslayer Orange?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Fire Orange is more muted than Trollslayer Orange.

Can I use Trollslayer Orange instead of Fire Orange?

The same difference applies the other way round: Trollslayer Orange is 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.