ΔE 4.6, very close: most people won’t see a difference side by side. Russet Brown is a little darker, cooler than Wyldwood. They are different kinds of paint: Citadel Wyldwood is a one-coat contrast-style paint and Reaper Russet Brown is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 5). Russet Brown is a little darker, cooler than Wyldwood. They are different kinds of paint.
The same difference applies the other way round: Wyldwood 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.
See Wyldwood on the colour wheel See Russet Brown on the colour wheel
All matches: Wyldwood equivalents · Russet Brown equivalents