Wyldwood vs Seraph Red

How close are they?

ΔE 21.5, loose: different enough that you should pick on purpose. Seraph Red is much more saturated, cooler than Wyldwood.

Can I use Seraph Red instead of Wyldwood?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Seraph Red is much more saturated, cooler than Wyldwood.

Can I use Wyldwood instead of Seraph Red?

The same difference applies the other way round: Wyldwood is much more muted, 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.