Hello,
There are no API's to alter the colours at runtime or for that matter any properties other than the object size and location and other basic properties.
The engine CR has always used to create charts is/was made by 3D Graphics.... We've never had any access into the chart properties through code. At one time you could get their Development Kit which gave you access but I don't believe it works any more due to the version we embed has not been updated in years and 3D no longer supports it.
You can set them in the Report Designer only.
Don