I am a bit curious, why the image has the wrong plane order in the first place?
Do you load the image from file, or is it acquired from a camera? If it comes from a camera, maybe the acquisition device isn’t configured correctly.
Anyway, you can use the SwapChannels() method from the 
Foundation package as follows:
var newImg = Stemmer.Cvb.Foundation.ConvertColorSpace.SwapChannels(img, new int[] {2, 1, 0} );
The array defines the new layout. So with the array { 2, 1, 0 }, an RGB image would be rearranged to BGR plane order.
I hope this helps!
Thomas