Sunpetal vs Serpent Eye Yellow

How close are they?

ΔE 6.4, close: similar, with a visible difference side by side. Serpent Eye Yellow is a little darker, more muted than Sunpetal.

Can I use Serpent Eye Yellow instead of Sunpetal?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Serpent Eye Yellow is a little darker, more muted than Sunpetal.

Can I use Sunpetal instead of Serpent Eye Yellow?

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