Ваш индикатор выполнения имеет стиль, соответствующий вашей текущей теме Windows.Если вы запускаете свое приложение в Windows 7 с темой Aero, индикатор выполнения будет выглядеть соответствующим образом.
Если вы хотите, чтобы оно всегда выглядело одинаково (независимо от того, какая тема Windows выбрана), вам нужно будет определить свою собственнуюстиль для индикатора выполнения.
Вот стиль из темы Aero Normal Color:
<LinearGradientBrush x:Key="ProgressBarBorderBrush"
EndPoint="0,1"
StartPoint="0,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#B2B2B2"
Offset="0"/>
<GradientStop Color="#8C8C8C"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarBackground"
EndPoint="1,0"
StartPoint="0,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#BABABA"
Offset="0"/>
<GradientStop Color="#C7C7C7"
Offset="0.5"/>
<GradientStop Color="#BABABA"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarTopHighlight"
StartPoint="0,0"
EndPoint="0,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#80FFFFFF"
Offset="0.05"/>
<GradientStop Color="#00FFFFFF"
Offset="0.25"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarGlassyHighlight"
StartPoint="0,0"
EndPoint="0,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#50FFFFFF"
Offset="0.5385"/>
<GradientStop Color="#00FFFFFF"
Offset="0.5385"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarIndicatorGlassyHighlight"
StartPoint="0,0"
EndPoint="0,1">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#90FFFFFF"
Offset="0.5385"/>
<GradientStop Color="#00FFFFFF"
Offset="0.5385"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<RadialGradientBrush x:Key="ProgressBarIndicatorLightingEffectLeft"
RadiusX="1"
RadiusY="1"
RelativeTransform="1,0,0,1,0.5,0.5">
<RadialGradientBrush.GradientStops>
<GradientStop Color="#60FFFFC4"
Offset="0"/>
<GradientStop Color="#00FFFFC4"
Offset="1"/>
</RadialGradientBrush.GradientStops>
</RadialGradientBrush>
<LinearGradientBrush x:Key="ProgressBarIndicatorLightingEffect"
StartPoint="0,1"
EndPoint="0,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#60FFFFC4"
Offset="0"/>
<GradientStop Color="#00FFFFC4"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<RadialGradientBrush x:Key="ProgressBarIndicatorLightingEffectRight"
RadiusX="1"
RadiusY="1"
RelativeTransform="1,0,0,1,-0.5,0.5">
<RadialGradientBrush.GradientStops>
<GradientStop Color="#60FFFFC4"
Offset="0"/>
<GradientStop Color="#00FFFFC4"
Offset="1"/>
</RadialGradientBrush.GradientStops>
</RadialGradientBrush>
<LinearGradientBrush x:Key="ProgressBarIndicatorDarkEdgeLeft"
StartPoint="0,0"
EndPoint="1,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#0C000000"
Offset="0"/>
<GradientStop Color="#20000000"
Offset="0.3"/>
<GradientStop Color="#00000000"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarIndicatorDarkEdgeRight"
StartPoint="0,0"
EndPoint="1,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#00000000"
Offset="0"/>
<GradientStop Color="#20000000"
Offset="0.7"/>
<GradientStop Color="#0C000000"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ProgressBarIndicatorAnimatedFill"
StartPoint="0,0"
EndPoint="1,0">
<LinearGradientBrush.GradientStops>
<GradientStop Color="#00FFFFFF"
Offset="0"/>
<GradientStop Color="#60FFFFFF"
Offset="0.4"/>
<GradientStop Color="#60FFFFFF"
Offset="0.6"/>
<GradientStop Color="#00FFFFFF"
Offset="1"/>
</LinearGradientBrush.GradientStops>
</LinearGradientBrush>
<Style x:Key="{x:Type ProgressBar}"
TargetType="{x:Type ProgressBar}">
<Setter Property="Foreground"
Value="#01D328"/>
<Setter Property="Background"
Value="{StaticResource ProgressBarBackground}"/>
<Setter Property="BorderBrush"
Value="{StaticResource ProgressBarBorderBrush}"/>
<Setter Property="BorderThickness"
Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ProgressBar}">
<Grid Name="TemplateRoot"
SnapsToDevicePixels="true">
<Rectangle Fill="{TemplateBinding Background}"
RadiusX="2"
RadiusY="2"/>
<Border Background="{StaticResource ProgressBarGlassyHighlight}"
Margin="1"
CornerRadius="2"/>
<Border BorderBrush="#80FFFFFF"
Background="{StaticResource ProgressBarTopHighlight}"
BorderThickness="1,0,1,1"
Margin="1"/>
<Rectangle Name="PART_Track"
Margin="1"/>
<Decorator x:Name="PART_Indicator"
HorizontalAlignment="Left"
Margin="1">
<Grid Name="Foreground">
<Rectangle x:Name="Indicator"
Fill="{TemplateBinding Foreground}"/>
<Grid x:Name="Animation" ClipToBounds="true">
<Rectangle x:Name="PART_GlowRect" Width="100"
Fill="{StaticResource ProgressBarIndicatorAnimatedFill}"
Margin="-100,0,0,0"
HorizontalAlignment="Left">
</Rectangle>
</Grid>
<Grid x:Name="Overlay">
<Grid.ColumnDefinitions>
<ColumnDefinition MaxWidth="15"/>
<ColumnDefinition Width="0.1*"/>
<ColumnDefinition MaxWidth="15"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Rectangle x:Name="LeftDark"
Grid.RowSpan="2"
Fill="{StaticResource ProgressBarIndicatorDarkEdgeLeft}"
RadiusX="1"
RadiusY="1"
Margin="1,1,0,1"/>
<Rectangle x:Name="RightDark"
Grid.RowSpan="2"
Grid.Column="2"
RadiusX="1"
RadiusY="1"
Fill="{StaticResource ProgressBarIndicatorDarkEdgeRight}"
Margin="0,1,1,1"/>
<Rectangle x:Name="LeftLight"
Grid.Column="0"
Grid.Row="2"
Fill="{StaticResource ProgressBarIndicatorLightingEffectLeft}"/>
<Rectangle x:Name="CenterLight"
Grid.Column="1"
Grid.Row="2"
Fill="{StaticResource ProgressBarIndicatorLightingEffect}"/>
<Rectangle x:Name="RightLight"
Grid.Column="2"
Grid.Row="2"
Fill="{StaticResource ProgressBarIndicatorLightingEffectRight}"/>
<Border x:Name="Highlight1"
Grid.RowSpan="2"
Grid.ColumnSpan="3"
Background="{StaticResource ProgressBarIndicatorGlassyHighlight}"/>
<Border x:Name="Highlight2"
Grid.RowSpan="2"
Grid.ColumnSpan="3"
Background="{StaticResource ProgressBarTopHighlight}"/>
</Grid>
</Grid>
</Decorator>
<Border BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
CornerRadius="2"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="Orientation"
Value="Vertical">
<Setter TargetName="TemplateRoot"
Property="LayoutTransform">
<Setter.Value>
<RotateTransform Angle="-90"/>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsIndeterminate"
Value="true">
<Setter TargetName="LeftDark"
Property="Visibility"
Value="Collapsed"/>
<Setter TargetName="RightDark"
Property="Visibility"
Value="Collapsed"/>
<Setter TargetName="LeftLight"
Property="Visibility"
Value="Collapsed"/>
<Setter TargetName="CenterLight"
Property="Visibility"
Value="Collapsed"/>
<Setter TargetName="RightLight"
Property="Visibility"
Value="Collapsed"/>
<Setter TargetName="Indicator"
Property="Visibility"
Value="Collapsed"/>
</Trigger>
<Trigger Property="IsIndeterminate"
Value="false">
<Setter TargetName="Animation"
Property="Background"
Value="#80B5FFA9"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Поместите этот код в файл Themes/Generic.xaml
в вашем приложении, и ваши индикаторы выполнения всегда будутесть этот стиль.