Q:

How to set background color of button in WPF?

How to set the background color of a button in xaml?
It can't be much harder than 
<Button Margin="2" Background ="LightGreen" ....>

But this does not work...for the avoidance of confusion, button here is System.Windows.Controls.Button
Edit
I forgot to mention that I use DevExpress's ThemeManager but did not think that would cause issues as per DevExpress they do not style the standard Windows Buttons...apparently they do, however, which basically makes it impossible to change the background color of a button without some major work...

A:

According to documentation:

DevExpress provides multiple themes that can be applied to all
  DevExpress controls for WPF and some standard controls (GroupBox,
  ScrollViewer, Scroll, RadoiButton, Button, ListBox, Slider,
  TabControl, Separator, ToggleButton, RepeatButton, Label, ListBoxItem,
  TabItem, ToolTip, etc).

As you can see the Button control is listed here. But then in documentation it is said that you can disable theme of individual control by setting ThemeName attribute to None. So, you can just disable the theme for button or for some of its parent containers and use your own style.
Here is example:
<Button Margin="2" Background="LightGreen" dx:ThemeManager.ThemeName="None" ...>

A:

Try this:
yourBtn.Background = new SolidColorBrush(Colors.Green);

Or in XAML:
<Window.Resources>
   <SolidColorBrush x:Key="BG" Color="Green"/>
</Window.Resources>

<Button Background="{DynamicResource BG}"></Button>

