Ah, try changing them to self.MouseEnter = function(sender,args) and self.MouseLeave = function(sender,args) ?
This is what I have in my plugin:
Code:
self.MouseEnter = function(sender, args)
self:SetBackColor(self.bgColor);
end
self.MouseLeave = function(sender, args)
self:SetBackColor(Turbine.UI.Color(0,0,0,0));
end