How to change the Background color of a RadControl in runtime?

[Di]

I have two radcontrols:
<telerik:RadMaskedNumericInput Name="txtC" Value="{x:Null}" IsClearButtonVisible="False" Height="30" Width="50" Mask="###" Placeholder=" " HorizontalContentAlignment="Right" HorizontalAlignment="Left" VerticalContentAlignment="Center" ValueChanged="txtC_ValueChanged" />

and I need to know how to change the background color according to the numbers the user is going to type.
eg: 

if (!string.IsNullOrWhiteSpace(txtAltura.Text))
{
   txtC.Background = "Green";
   // or
   txtC.Background = ColorNames.Green;
}

I already checked other solutions with System.Windows.Media.BrushConverter, but it doesn't appear in my codebehind, even using the namespace. I am using VS 2010.

Di.

[Shinu]

Hi Di,

Please have a look at the sample C# code I tried to set the background of RadRichTextBox.

C#:

radRichTextBox.Background = new SolidColorBrush(Colors.Green);

Also you can directly modify the background color of the active presenter like this:

C#:

((Control)radRichTextBox.ActiveEditorPresenter).Background = new SolidColorBrush(Colors.Yellow);

Thanks,
Shinu.

[Di]

Thanks Shinu.