Indeed... the XamNumericEditor below the CellValuePresenter has FG color ...white (well, it's light grey actually... but looks white ;-)... and this value is flagged as "Inherited in Snoop's Value Source.  Inherited from where?   The object (CVP) at higher level  sets it red...(BTW... I am not expert in this stuff, forgive me if say something dumb!).  If I track back up the visual tree, I eventually see DataRecordPresenter with Foreground FontControlBrush set to the white(grey) color... but that's as expected... and wanted.  I do want (most) of my grid foreground white...  but added  this code to achieve the red negatives on just two fields

			Style redForegroundStyle  = mainpage.Resources["CVP_RedField"]  as Style;
			Style blueForegroundStyle = mainpage.Resources["CVP_NormalField"] as Style;
			dg1.DefaultFieldLayout.Fields["Profit"].Settings.CellValuePresenterStyleSelector =
				new CVPStyleSelector_Field(redForegroundStyle, blueForegroundStyle);
			dg1.DefaultFieldLayout.Fields["CNP"].Settings.CellValuePresenterStyleSelector =
				new CVPStyleSelector_Field(redForegroundStyle, blueForegroundStyle);

Plus this code... taken pretty much straight out of the Help page on Conditional Formatting:

		internal class CVPStyleSelector_Field : StyleSelector
		{
			private Style _redStyle;
			private Style _normalstyle;

			internal CVPStyleSelector_Field(Style redStyle, Style normalstyle)
			{
				this._redStyle    = redStyle;
				this._normalstyle = normalstyle;
			}

			public override Style SelectStyle(object item, DependencyObject container)
			{
				bool isneg = (0 > decimal.Parse(item.ToString()));

				if (isneg)
				{
					return _redStyle;
				}
				else
				{
					return _normalstyle;
				}
			}
		}

Finally... here's my XAML code:

  <Grid x:Name="mainpage" Margin="0,10,0,00" Height="Auto" VerticalAlignment="Stretch">
      <Grid.Resources>

        <Style x:Key="CVP_RedField" TargetType="{x:Type dp:CellValuePresenter}">
          <Setter Property="Foreground" Value="Red" />
        </Style>
        <Style x:Key="CVP_NormalField" TargetType="{x:Type dp:CellValuePresenter}">
          <Setter Property="Foreground" Value="Blue" />
        </Style>

I kinda said already... I don't really even WANT XamNumericEditor at all... NO EDITS... I just want to display the value red if negative - period.  In fact, I really WANT to get rid of the NumericEditor control... it just messes up my display when you click on it (I don't need/want that).

The other frustration for me is this:  I used exactly the same code in a standalone WPF app I cut... and it works perfectly.   Only difference is my real "app" is an embedded add-on in my trading platform... rather than a standalone WPF app.  See next pic...

Thankyou for your help...

THANKYOU!  I have been banging my head on the wall for weeks trying to resolve this... you have solved both my issues nicely.

Extremely grateful!