ColorPicker.xaml

<UserControl x:Class="ColorPicker"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:ColorPicker"
             mc:Ignorable="d" Height="269" Width="400">
    <StackPanel x:Name="PickerPanel" Orientation="Vertical" Background="White">
        <Grid HorizontalAlignment="Stretch" Height="210" MouseDown="RgbGradient_MouseDown">
            <Grid.Background>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="Black" Offset="1"/>
                    <GradientStop Color="White"/>
                    <GradientStop x:Name="MiddleStop" Color="#FF787878" Offset="0.5"/>
                </LinearGradientBrush>
            </Grid.Background>
        </Grid>
        <Grid x:Name="SpectrumGrid" Height="40" MouseLeftButtonDown="SpectrumGrid_MouseLeftButtonDown">
            
        </Grid>
        <TextBlock x:Name="HexCode" TextWrapping="Wrap"/>

    </StackPanel>
</UserControl>