ΔE 17.5, loose: different enough that you should pick on purpose. Slate Grey is a little lighter, much more muted than Wyldwood. They are different kinds of paint: Citadel Wyldwood is a one-coat contrast-style paint and Nocturna Models Slate Grey is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Slate Grey is a little lighter, much more muted than Wyldwood. They are different kinds of paint.
The same difference applies the other way round: Wyldwood is a little darker, much 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.
See Wyldwood on the colour wheel See Slate Grey on the colour wheel
All matches: Wyldwood equivalents · Slate Grey equivalents