How to compensate for red oversaturation and contrast increase? When uploading a video to Vimeo the video is transcoded by Vimeo and in the process red gets a bit more saturation and the contrast is increased a little.
As I chose Vimeo as my platform I have to live with that and hence compensate for it during my video production.
How would I determine the exact amount of red desaturation and contrast decrease? Can I overlay the screenshots somehow and calculate a difference? Is there maybe a plug-in for Premiere Pro that compares two videos and outputs a suggested colour correction?

I know I can do this by trial and error, but I'd rather have an automatic solution. 
Here's an image showing the effect:


Note the difference of skin tone between Safari and Vimeo HD file. The latter is the intended colour.
Unfortunately, even if you could get an exact amount of the difference, it is highly unlikely that adjusting by that amount will fix your problem.  Since a lossy compression is being used, the codec is deciding to alter the color to something that is more easily stored in a small space.  You will likely get a different color artifact if you try to correct for this one.  Your best bet would probably be to look in to the formats that Vimeo uses and try to encode it yourself such that Vimeo won't have to transcode it.  This would give you control over the compression itself and you might be able to use a better encoder that would maintain color more accurately.