Hi,
yes all Samplitude and Sequoia versions support skins from Ver5 onwards.
A lot of user skins were made around the Ver6 period and many still use them.
However, as features get added all the time, some buttons are missing from older skins. Still its ok if you know how to use the newer functions via right mouse menu for instance.
Of course each new Samplitude version come with a new skin so after a while you get a nice collection.
I've got around 10 skins loaded for easy changing.
Cheers
M