Hi igal a,
Please find attached a sample project that shows how to change MainPaletteColumnsCount and MainPaletteOrientation properties at runtime.
Note: these two properties MainPaletteColumnsCount and MainPaletteOrientation are used only when you want to define some custom palettes using the selector ItemsSource:
this.selector.MainPaletteColumnsCount = 3;
this.selector.MainPaletteOrientation = Orientation.Vertical;
this.selector.MainPaletteItemsSource = this.GetColors();
If you are using the build in palettes (this means that you do not specified any ItemsSource or set the MainPalette property to some of the build in palettes) then you do not have to apply orientation or columns count.
I hope that this will help you. Please let us know if you have any other questions or you need some more help.
the Telerik team