Luminous Orange vs Trollslayer Orange

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Trollslayer Orange is a little darker, cooler than Luminous Orange.

Can I use Trollslayer Orange instead of Luminous Orange?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Trollslayer Orange is a little darker, cooler than Luminous Orange.

Can I use Luminous Orange instead of Trollslayer Orange?

The same difference applies the other way round: Luminous Orange is a little lighter, 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.