TabsStudioDefaultTabStyle.xsl

<Style TargetType="TabsStudio:Tab" BasedOn="{StaticResource DefaultTabStyle}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TabsStudio:Tab}">
                <Grid>
                    <Border Name="Border" BorderBrush="#609ABA" BorderThickness="1,1,1,0" CornerRadius="3,3,0,0">
                        <ContentPresenter ContentSource="Header" Margin="12,2,12,2"/>
                    </Border>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsTabSelected" Value="True">
                        <Setter TargetName="Border" Property="Background">
              <Setter.Value>
                <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                    <GradientStop Color="#FCFDFE" Offset="0"/>
                    <GradientStop Color="#EBF3FC" Offset="0.2"/>
                    <GradientStop Color="#CEE4FA" Offset="1"/>
                </LinearGradientBrush>
              </Setter.Value>

                        </Setter>
                    </Trigger>
                    <Trigger Property="IsTabSelected" Value="False">
                        <Setter TargetName="Border" Property="Background">
              <Setter.Value>
                <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                    <GradientStop Color="#EAF4FC" Offset="0"/>
                    <GradientStop Color="#90AECE" Offset="1"/>
                </LinearGradientBrush>
              </Setter.Value>

</Setter>
                    </Trigger>

                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>
<Style TargetType="TabsStudio:CloseTabButton" BasedOn="{StaticResource DefaultCloseTabButtonStyle}">
    <Style.Triggers>
        <Trigger Property="IsTabSelected" Value="False">
            <Setter Property="Visibility" Value="Visible"/>
        </Trigger>
    </Style.Triggers>
</Style>