We are unable to reproduce the issue you are facing on our local tests. You can see from the image attached that the background is set without problems. I've managed to change the colors both programmatically and through Properties in Design mode. Here is how the colors were set programmatically:
radChart1.PlotArea.Appearance.FillStyle.MainColor = Color.White;
radChart1.PlotArea.Appearance.FillStyle.SecondColor = Color.LightBlue;
Have in mind that the FillStyle.FillType is set to Gradient by default.
Do you use by any reason another Skin than the Default one? If this is your case turn off SkinsOverrideStyles
property of the RadChart so that the Color changes will take effect.
All the best,
the Telerik team
Q3’10 SP1 of RadControls for WinForms is available for download
; also available is the Q1'11 Roadmap
for Telerik Windows Forms controls.