This is an effect of the recording stage.
For most codecs the frames are encoded as 4:2:2 Y’CbCr which involves chroma subsampling. We use a shader for the pixel-format conversion which I’m working to improve at the moment – the current release is not perfect. If you can link to an image of a single frame or e-mail me one I can include it in our tests. I can also send you a new version of Recorder in a few days which it would be good to get feedback on – firstname.lastname@example.org
If you have them installed, you could see what results you get with Apple ProRes 4:4:4:4 or Sheer RGB[A] 8bf which will both take different paths. Sheer RGB[A] 8bf should be a perfect match for the source. You can download a trial of the codec at http://www.bitjazz.com/en/products/sheervideo/