Avalonia/src/Avalonia.Controls.ColorPicker/Themes/Simple/Simple.xaml

<Styles xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:converters="using:Avalonia.Controls.Converters">

  <Styles.Resources>
    <ResourceDictionary>

      <!-- Shared Resources -->
      <VisualBrush x:Key="ColorControlCheckeredBackgroundBrush"
                   TileMode="Tile"
                   Stretch="Uniform"
                   DestinationRect="0,0,8,8">
        <VisualBrush.Visual>
          <DrawingPresenter Width="8"
                            Height="8">
            <DrawingGroup>
              <GeometryDrawing Geometry="M0,0 L2,0 2,2, 0,2Z"
                               Brush="Transparent" />
              <GeometryDrawing Geometry="M0,1 L2,1 2,2, 1,2 1,0 0,0Z"
                               Brush="#19808080" />
            </DrawingGroup>
          </DrawingPresenter>
        </VisualBrush.Visual>
      </VisualBrush>

      <!-- Shared Converters -->
      <converters:EnumToBoolConverter x:Key="EnumToBoolConverter" />
      <converters:ToBrushConverter x:Key="ToBrushConverter" />
      <converters:CornerRadiusFilterConverter x:Key="LeftCornerRadiusFilterConverter" Filter="TopLeft, BottomLeft"/>
      <converters:CornerRadiusFilterConverter x:Key="RightCornerRadiusFilterConverter" Filter="TopRight, BottomRight"/>
      <converters:CornerRadiusFilterConverter x:Key="TopCornerRadiusFilterConverter" Filter="TopLeft, TopRight"/>
      <converters:CornerRadiusFilterConverter x:Key="BottomCornerRadiusFilterConverter" Filter="BottomLeft, BottomRight"/>
      <converters:CornerRadiusToDoubleConverter x:Key="TopLeftCornerRadiusConverter" Corner="TopLeft" />
      <converters:CornerRadiusToDoubleConverter x:Key="BottomRightCornerRadiusConverter" Corner="BottomRight" />

      <ResourceDictionary.MergedDictionaries>

        <!-- Primitives -->
        <ResourceInclude Source="avares://Avalonia.Controls.ColorPicker/Themes/Simple/ColorPreviewer.xaml" />
        <ResourceInclude Source="avares://Avalonia.Controls.ColorPicker/Themes/Simple/ColorSlider.xaml" />
        <ResourceInclude Source="avares://Avalonia.Controls.ColorPicker/Themes/Simple/ColorSpectrum.xaml" />

        <!-- Controls -->
        <!-- Note the ColorPicker and ColorView are currently unsupported in the simple theme -->
        <!-- These controls depend on fluent styles for TabControl, Button, TextBox, etc. -->

      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Styles.Resources>
</Styles>