Xfwm4 Window Decorations have the same color regardless of theme variant.

[mantacid]

The colors of the XFCE window decorations remain constant across all themes; the dark variants and the Nord variants both use the same grey for example.

A potential solution to this would be to use .xpm files in the xfwm4 theme, rather than .png, since the former can pick up the colors defined by the GTK color scheme.