I just noticed that the colour in the preview windows of Vegas Pro 14 is slightly duller than the original video.  After all these years I hadn't noticed, because it was so subtle, but now that I am getting into colour calibration, I can easily see it.  It happens with all files, video and graphics and I have compared it to other video editing suites which appear identical to the original video.

With the default settings, I can drag in a clip and it looks more muted then playing the file on a media player.  I can counter this by adding a +0.1 in the contrast panel, but it's not 100% accurate, but more importantly, why is this happening in the first place?

Is Vegas converting the colour space to something else during editing?

The rendered output appears to be okay and like the original video, but this makes adjustments difficult to predict.  Why is the preview so different?