I've always loved the Shiki-Colors series of themes since it first came out during the summer of 2008. But since GTK3 came out sometime last year, it has caused all GTK3 apps to have that very annoying Windows 9x look to them. But thankfully, there's Alex Vanderpol's (aka "Karashata") Zukitwo-Colors, which is the GTK3-compatible successor to Shiki-Colors.
However, there's one slight problem for us Xfce users: Karashata didn't include any Xfwm themes with them. Therefore, I decided to take matters into my own hands and take the old Shiki-Colors Xfwm themes (the regular, easy, and dust versions) and darken them in order to match the menu colors of the Zukitwo-Colors series of themes.
And now, once again, you have the nice coherent look (albeit darker than the original, of course) of the Shiki-Colors series of themes AND full GTK3 compatibility. For your convenience, I've also included links to the Zukitwo-Colors series of GTK 2/3 themes and GNOME-Colors series of icon themes. Enjoy! :-)