Yriel Yellow vs Marduk Yellow

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Marduk Yellow is a little lighter than Yriel Yellow.

Can I use Marduk Yellow instead of Yriel Yellow?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Marduk Yellow is a little lighter than Yriel Yellow.

Can I use Yriel Yellow instead of Marduk Yellow?

The same difference applies the other way round: Yriel Yellow is a little darker.

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.