[Shawn Jarrett]

Ok, I have figured out how to do this from trial and error. (I am using Vegas Pro).

1. chroma key out the blue in clip, revealing the desired background behind it, select “Cut” composite mode.
2 Render as 3mps Quicktime, prog scan, PNG format, 32bpp color.
3 Import this file back into project. Select properties, Media, Alpha Channel, premultiplied (or Straight).
4 ensure blue chroma key is now off & composite set to source alpha
5 Have the clip to be green chroma keyed beneath this imported clip & the green’s desired background beneath that.
6 Wollah! The blue & green areas of the original clip now have their own seperate image showing. 🙂