WPF: how to get LinearGradientBrush color exactly like other

Question

I want to get this kind of form color:

This is what i have try:

<Border.Background>
    <LinearGradientBrush StartPoint="0,0" EndPoint="1,1" >
        <GradientStop Color="Black" Offset="0.5" />
        <GradientStop Color="Red" Offset="1.0" />
    </LinearGradientBrush>
</Border.Background>

Answer 1

Like this?

<LinearGradientBrush StartPoint='1,0' EndPoint='0,1' >
    <GradientStop Color='#FF663F51' Offset='0' />
    <GradientStop Color='#FF320E42' Offset='1' />
</LinearGradientBrush>