I've uploaded a nonpublic clip of a closeup of a woman onto YouTube, that I'm using in a horror film. I'm looking for how to start the clip in full color then have it drain out of the face as it progresses to the end. Not with a hard line, rather a gradient type.
I'm not an expert on effects.
I'd suggest de-saturate the color via animate (Color Corrector)
Play with something like Bump Map to add some drama to the face as the color drains away.
This can be as easy as creating a copy of the clip,applying the "drained look" to it and using a vertical soft edged wipe between the two.
Or: the face area could be masked and the FX applied to that area only; again:copying and using the wipe...probably several more ways to achieve this in Vegas.
Hope this helps.
Ken