I am completely stumped. I've noticed recently that my imported images are not matching what is on my memory cards. I thought it was just my new R5 but it is also happnening with images I download into Bridge with my Mark IV and Mark III. They color matches at first but then completely desaturates...as if after it's processed in Bridge the thumbnail completely changes to a unsaturated version of the original image. When I hope in ACR it's still the unsaturated image. It's PERFECT in camera. PLEASE HELP! This is turning into an editing nightmare.
There are a HOST of things that could be causing this, but first let me state flat out that Bridge cannot change any setting. Bridge shows what the true settings should represent.
Things that can vary are what settings you set (intentionally or not) in Adobe Camera Raw, your computer, Photoshop, Lightroom, etc as all of those things can change settings.
Also, what you see "in the camera" is almost almost always a JPG representation of the image you just took and should not be used as a guide as to what the image will end up being. The reason for this is that (and I'm assuming you are taking raw images) cameras are not likely to be doing the demosaicing that's necessary to view a raw image. Rather, what's done is that a jpg is presented as the image so you have something to work with. However, since a jpg can only be an 8-bit image, and raw images can be anywhere from 12–14-bit images, the jpgs seldom if ever look like they will in ACR.
Another issue is what Profile you've set for any given image (intentionally or not). In ACR you can set many different profiles into an image that have nothing to do with their ACR adjustments in the Edit component in ACR. Below I've got a single image and I'm showing the viewing options for the Profiles featuring the options in the Adobe group and the Camera group (they are sequential in the Panel but I've placed them side-by-side for this display).
What it all boils down to is that there's little chance one can determine why you are seeing what you are seeing unless we have a better understanding as to what's been done (intentionally or not) to the images.
Good luck, I hope I've given you some thoughts as for what to look for.