If you just want to change the colour of the selection, then the easiest way is to set the solidcolorbrush as a resource on your Listbox:
<ListBox x:Name="AssetTypeListBox" SelectionMode="Multiple">
<ListBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="#F15025"/>
<SolidColorBrush x:Key="{x:Static SystemColors.InactiveSelectionHighlightBrushKey}" Color="#F15025"/>
</ListBox.Resources>
<ListBox.ItemsPanel >
<ItemsPanelTemplate >
<UniformGrid Columns="6"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
If you're wanting to customise the style of the selection of an item in the listbox, such as changing the selection colour or completely restyling the look of a selected item, you need to look at the ItemContainerStyle property.
The ItemsPanelTemplate doesn't affect this - it simply sets the ItemsControl type that should layout and present the items - such as a StackPanel or UniformGrid.
The basic hierarchy (with a pinch of salt) of a ListBox is:
- ListBox
- ItemsPanelTemplate (StackPanel by default)
- ItemsContainerStyle (Selection highlighting is here)
- ItemTemplate (You define the content of your list item here)
The differences between ItemTemplates and ItemsContainerStyle are covered here:
What's the difference between ItemTemplate and ItemContainerStyle in a WPF ListBox?