Also, one other thing - did you also check the color profile that you were filming in? D-Log vs. Cinelike vs. Art vs. Truecolor vs. others, all have specific adjustments and will greatly affect the color "output" of your video/photos. Check it out here if you want a comparison:
(or 1,000 other videos on Youtube)
It's hard to say anything without knowing your specific settings prior to the upgrade and after. You'd also have to be certain that all settings were identical to compare equivalent shots. ISO, shutter speed, white balance, etc. - all need to be identical. Moreover, auto settings are not equivalent settings. Even a normal DSLR camera set to auto can change the "look" of a shot (and the internal settings), depending on the environmental circumstances. You can have everything set to "auto" and take two sequential shots, 30 seconds apart, and have them look entirely different. A different orientation, a cloud passing by, a reflection, etc. all can change the settings in the camera and the Mavic's camera is no different.
Settings on "auto" are asking the camera to adjust its internal settings to adapt to changing conditions (if it weren't, you could just place the camera on one group of settings for everything and they would always work, but that's not how things work). Therefore, any changes in environmental conditions (even momentary) require the camera to adjust its own settings to match what it "thinks" are appropriate settings. Most times, the camera does a fine job. Many times however, it has to make compromises or selects something it considers better than another. This is why professional photographers (or those wanting to do more than just point-and-shoot) never use anything but manual settings. The Mavic is no different.
So on "auto", the Mavic can select what it thinks are appropriate settings for the correct adjustments to adapt to a specific shot. It can do the same from moment to moment. Or firmware to firmware. I do not know if DJI actually adjusted the algorithm for its "auto" settings for the new firmware - though it's not noted in the release notes for the new version (
New Mavic Pro Firmware Released (22/08/2017)), so I doubt it, but it's not impossible. Take it off auto and make the appropriate manual settings yourself. Then no algorithm will be making the decisions for you and you can film as you wish to see it.