Hello,
I do not know about “gnome-color-chooser”. Thanks @stevecook172001
After some search, there is no GTK 3 version.
But I found this tools which seems to be GTK 2 and GTK 3 compatible.
gtk-theme-config: on launchpad.net
Some screen captures: http://www.webupd8.org
Not tested yet and don’t know if it will work with Mate Theme.
Kr,