The ConvertTo method changes the color mode of a bitmap.
Examples:
The following VBA example converts all bitmaps on the active page to the RGB color mode.
Sub Test()
Dim s As Shape
For Each s In ActivePage.Shapes
If s.Type = cdrBitmapShape Then
If s.Bitmap.Mode <> cdrRGBColorImage Then
s.Bitmap.ConvertTo cdrRGBColorImage
End If
End If
Next s
End Sub